Polymers doi: 10.3390/polym18222839

Authors: Kameliia Rashitova Semen Goreninskii Oksana Kukartceva Natalia Bobrysheva Mikhail Osmolowsky Mikhail Voznesenskiy Evgeny Bolbasov Andrey Yaroslavtsev Olga Osmolovskaya

In this work, we synthesized Cr3+-doped Mg-Al layered double hydroxides by co-precipitation, varying reagent addition sequence and with or without NaCl. The sample prepared by simultaneous addition without NaCl exhibited the highest specific surface area (103 m2·g−1) and narrowest band gap and was selected for incorporation into electrospun poly(vinylidene fluoride-co-tetrafluoroethylene) (VDF-TeFE) fibers at 0.1, 0.5, and 1.0 wt.%. The 0.5 wt.% composite showed optimal photoinduced Pb2+ removal: 80% after 2 h UV irradiation compared to 50% after 4 h in the dark and 17% for pristine polymer. Scavenger experiments revealed different mechanisms. Pristine polymer removal proceeds via electron-driven reduction to metallic lead (Pb0), while the composite follows a superoxide-mediated pathway, with no Pb0 detected on the surface. Analysis of the bare nanopowder after Pb2+ removal revealed formation of hydrocerussite (Pb3(CO3)2(OH)2). We suggest that UV irradiation can activate defects on the embedded particles, creating local charge domains that drive Pb2+ migration to the particle–polymer interface, where superoxide radicals locally increase pH and promote precipitation as hydrocerussite. This work demonstrates a photoinduced sorption pathway for stable lead immobilization.

Polymers doi: 10.3390/polym18222837

Authors: Rita Zhumatay Şemsi Yazıcı Süleyman Özen Ali Mardani

Recycled construction-waste fine aggregates and polypropylene (PP) fibers can modify the ambient and post-cooling mechanical responses of geopolymer mortars. However, their effects require separate assessment, particularly regarding the trade-off between ambient mechanical properties and post-heating performance. This study investigated high-calcium fly ash-based geopolymer mortars incorporating recycled brick–tile, ceramic, and hybrid brick–tile/ceramic fine aggregates, together with a separate PP-fiber series containing 0.25%, 0.50%, and 0.75% fiber by fly-ash mass. Flexural and compressive strengths were measured at 3, 7, and 28 days, and 28-day specimens were exposed to 500 and 750 °C. Residual mechanical properties were evaluated after cooling, while SEM-EDS was used to examine thermally induced microstructural and local compositional changes. Replacing limestone with single recycled aggregates reduced ambient strength, whereas the hybrid mixture partly recovered this loss, reaching 19.37 MPa in compression and 5.41 MPa in flexure at 28 days. The 0.75% PP mixture achieved the highest ambient flexural strength (9.78 MPa), 26.0% above the control, although all fiber-reinforced mixtures showed lower compressive strength. Thermal exposure changed the relative ranking of the mixtures: at 500 °C, ceramic and hybrid mixtures increased compressive strength by 94.5% and 65.7%, respectively, while at 750 °C the brick–tile mixture reached 34.91 MPa. The results demonstrate that mixtures with lower ambient strength can exhibit favorable residual performance after severe thermal exposure, highlighting the importance of jointly evaluating recycled aggregate type and PP-fiber dosage for geopolymer mortars intended for thermally demanding conditions.

Polymers doi: 10.3390/polym18222838

Authors: Junaid Saleem Zubair Khalid Baig Moghal Gordon McKay

Mixed polyolefin waste can be treated by dissolution-assisted recycling or pyrolysis, yet comparisons are often confounded by different feedstocks, pretreatment, system boundaries, and product functions. This study presents a harmonised process-level life cycle assessment of dissolution-assisted recycling and pyrolysis of a 50:50 post-consumer high-density polyethylene/polypropylene blend. Both routes receive 1 kg of clean, dry polymer after identical transport and pretreatment. The dissolution route circulates xylene and yields recycled pellets; pyrolysis yields oil, char, and non-condensable gas. Seventeen selected ReCiPe 2016 midpoint (H) indicators were evaluated. Within this treatment-based boundary, pyrolysis had lower impacts in all 17 categories. Climate change impacts were 1.643 and 0.663 kg CO2-eq per functional unit for dissolution-assisted recycling and pyrolysis, respectively, a 59.6% lower result for pyrolysis. Electricity, fresh-xylene production, and solvent-residue treatment were key dissolution burdens, and pyrolysis was predominantly electricity-driven. Extending xylene reuse to seven cycles while reducing route-specific electricity by 10% lowered dissolution’s climate change impact to 1.293 kg CO2-eq per functional unit, 21.3% below its base case, without changing the ranking. Reducing polymer recovery to 98% and 95% increased the base-case climate change impact of dissolution-assisted recycling by 1.1% and 2.8%, respectively. Separate sensitivity analyses examined pyrolysis process energy, off-gas utilisation, electricity sources, geographical assumptions, and routine solvent deficit and distillation recovery, varied independently. The comparison is limited to treatment of the same plastic-waste input and, therefore, excludes avoided-product credits and downstream conversion of pyrolysis products into new polymers. The fate of routine xylene losses was not measured, which limits interpretation of the toxicity and photochemical-ozone indicators. These results identify solvent containment, reuse, and electricity efficiency as priorities for dissolution-assisted recycling, and process-energy efficiency for pyrolysis, while underscoring the need for harmonised downstream comparisons to assess circularity.

Polymers doi: 10.3390/polym18222836

Authors: Şenol Şahin Emir Haktan Ünal Ferhat Akpınar

Finite element analysis predicts the response of filled polymers only when the constitutive model suits the material and its parameters are reliably identified. This study evaluates the applicability and limits of the Bergström–Boyce (BB) model for calcium carbonate (CaCO3)-filled polypropylene block copolymer (PPB). Neat PPB and composites with 10, 20, and 30 vol% CaCO3 are tested in uniaxial tension at five strain rates and characterized by dynamic mechanical analysis and differential scanning calorimetry. The BB parameters are identified by a multi-start evolution strategy with trust-region refinement, and their identifiability is assessed by sensitivity, Fisher-information, profile, and multi-start analyses. The filler raises Young’s modulus from 1523 to 3716 MPa while reducing ductility and rate sensitivity. The model reproduces the tensile response with R2 = 0.94–0.99 in calibration and 0.96–0.99 at the two withheld strain rates, whereas the viscous-network locking stretch is unidentifiable. Without refitting, the parameters predict the stress relaxed in 1 h within a median factor of 1.3. Predicted creep, however, inherits the stress exponent of the flow rule and approaches the measurements only near 11–17 MPa. Identifiability established in tension is thus local to the calibration conditions; sustained loading requires creep or relaxation data at the service stress.

Polymers doi: 10.3390/polym18222835

Authors: Minge Zheng Xingwei Jiang Fuzai Niu Lingfeng Yu Tao Wang Huayang Yu

The asphalt pavements on the Qinghai–Tibet Plateau suffer from severe performance degradation under the coupling effect of intense ultraviolet radiation and cyclic low temperature. Crumb rubber modified asphalt (CRMA) is regarded as a durable pavement material suitable for alpine high-altitude regions, yet the viscoelastic damage mechanism of CRMA under radiation–low-temperature coupled aging remains unclear. In this study, six groups of CRMA specimens with two rubber particle sizes (40 mesh and 80 mesh) and three dosages (10%, 15%, and 20%) were prepared. A laboratory accelerated aging device was adopted to simulate plateau coupled aging with ultraviolet irradiation durations of 0, 4, 6, and 12 months, while rolling thin-film oven aging (RTFO), a pressure aging vessel (PAV), and ozone aging were set as control groups. Dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were conducted to characterize the high-temperature rutting resistance and low-temperature crack resistance of aged CRMA, and the Burgers viscoelastic constitutive model was employed to quantitatively fit the low-temperature creep curves and analyze the evolution law of constitutive parameters. The results show that prolonged ultraviolet radiation aggravates the hardening and embrittlement of CRMA synergistically: the complex modulus and rutting factor increase continuously, while the phase angle decreases, which improves high-temperature deformation resistance but deteriorates low-temperature performance; the creep stiffness modulus rises, and the creep rate declines, indicating a weakened stress relaxation capacity and elevated cracking risk at low temperatures. Thermal oxidation pre-aging and ozone aging further amplify the coupled aging damage. Increasing the crumb rubber dosage from 10% to 20% simultaneously optimizes the high- and low-temperature durability of aged CRMA. Under the same dosage, 40-mesh coarse rubber powder better enhances the anti-rutting performance at high temperatures, whereas 80-mesh fine rubber powder presents superior low-temperature crack resistance, which is hypothesized to originate from greater interfacial interaction with the asphalt matrix. The Burgers model achieves outstanding fitting accuracy for all creep curves with the coefficient of determination R2 > 0.994, and the four model parameters E1, E2, η1, and η2 can quantitatively reveal the evolution of instantaneous elasticity, delayed elasticity, and viscous flow behavior during aging. For pavement material design in plateau regions, 40-mesh CRMA with a 20% dosage is recommended for high-temperature rutting control, and 80-mesh CRMA with a 20% dosage is preferred to mitigate low-temperature thermal cracking. This work provides theoretical support for the performance evaluation and material optimization of long-life rubber asphalt pavements serving in extreme plateau environments.

Polymers doi: 10.3390/polym18222834

Authors: Junaid Saleem Zubair Khalid Baig Moghal Gordon McKay

Selecting a recycling route for post-consumer polyolefins requires distinguishing energy savings from purchased-input cost reductions, yet the two are often assumed to coincide. Here, mechanical recycling and pyrolysis of high-density polyethylene (HDPE) and polypropylene (PP) were compared to test whether equal energy demand implies equal operating cost. The functional unit (FU) covered pretreatment and conversion of waste supplying 1 kg of clean, dry polymer. Calculated extrusion electricity and an engineering-based pyrolysis inventory supported energy and recurring-cost models. Across the three cases, base cumulative energy demand was 12.8–14.2 MJ/FU and recurring costs 0.030–0.033 USD/FU. Direct-energy parity occurred at extrusion electricity of 0.7766 kWh/kg, but cost parity at base prices occurred at 0.8431 kWh/kg. Between these values, mechanical recycling used more energy but cost less, because avoided purge nitrogen outweighed its additional electricity and cooling-water costs. HDPE (0.838 kWh/kg) fell within this interval, whereas for PP (0.711 kWh/kg) mechanical recycling was favored on both energy and cost. Jointly varying conversion electricity, nitrogen consumption and prices reversed the cost orderings for both polymers within the tested ranges. Lower energy demand therefore does not guarantee lower operating cost; routes should be compared on both bases. These results concern processing only, not product equivalence or plant profitability.

Polymers doi: 10.3390/polym18222833

Authors: Mirjana Petronijević Sanja Panić Jelena Tanasić Aleksandra Cvetanović Kljakić Biljana Lončar Svetlana Đogo Mračević Slavica Ražić

Magnetite–geopolymer composites have primarily been investigated as adsorbents, whereas their use as enzyme carriers offers a catalytic route for phenol removal. Here, a magnetic allophane–kaolin geopolymer biofunctionalized with tangerine peel extract was developed as a support for covalent horseradish peroxidase (HRP) immobilization. This study combines this material platform with an integrated assessment of phenol and halogenated phenol removal, operational stability, water matrix effects, and post-treatment phytotoxicity. This study evaluates the obtained T-M-AK-G-HRP as a recoverable biocatalyst and assesses the contribution of biofunctionalization by comparing it with pristine and non-biofunctionalized magnetic geopolymer supports. At an initial phenol concentration of 10 mg/L, immobilized HRP (0.7 U/mL, n(H2O2)/n(phenol) = 1:1) achieved complete removal within 1 h, whereas the support showed no measurable phenol adsorption under the tested conditions. Removal efficiencies of 72–95% were obtained in spiked real-water matrices after 2 h. At 25 mg/L, removal efficiencies for phenol and derivatives ranged from 80.2% to 96.6% after 1 h. The biocatalyst was magnetically recovered for repeated use, achieving 56.6% phenol removal in the fourth treatment cycle. Treatment also reduced phytotoxicity in the Allium cepa assay. These findings extend magnetic geopolymer applications from pollutant adsorption to enzyme-mediated treatment and identify biofunctionalization as a strategy for improving biocatalyst reusability.

Polymers doi: 10.3390/polym18222832

Authors: Alexia-Ecaterina Cârstea Lucian-Toma Ciocan João Malta Barbosa Ronaldo Hirata Marina Imre

Reconstruction of craniomaxillofacial (CMF) bone defects remains demanding because the defects are irregular, three-dimensionally curved and functionally and aesthetically critical. Autologous bone carries donor-site morbidity, and most alloplastic and tissue-engineered alternatives are static, so gaps at the implant-bone interface frequently persist. Shape-memory polymers (SMPs) and four-dimensional (4D) printing introduce a different paradigm, in which a construct is programmed into a temporary shape and recovers a defect-conforming geometry in response to body temperature, near-infrared light, magnetic fields or water. Following the Scale for the Assessment of Narrative Review Articles (SANRA), PubMed/MEDLINE, Scopus and Web of Science were searched for literature published up to September 2026. This narrative review summarizes the clinical problem of CMF reconstruction, the molecular basis and programming of biomedical SMPs, the main polymer families, triggering strategies and fabrication routes. Preclinical evidence on self-fitting poly(epsilon-caprolactone) scaffolds, polylactide composites, photothermal and magnetic constructs, morphing membranes and alveolar socket fillers is critically discussed, together with degradation, osteoimmunomodulation, vascularization, sterilization, storage stability and regulation. Current evidence remains largely preclinical, limited to in vitro and small-animal studies. Finally, knowledge gaps and research priorities are outlined to guide the clinical translation of shape-memory and 4D-printed polymers in CMF surgery.

Polymers doi: 10.3390/polym18222831

Authors: Gadir S. Aliev Marina A. Evdokimenko Kirill A. Kirshanov Nadezhda A. Lobanova Anton M. Pogorely Roman V. Toms Alexander Y. Gervald

Open-loop recycling can valorize polylactide (PLA) when mechanical recycling or industrial composting is impractical. This study links PLA glycolysis modeling to UV-curable pressure-sensitive adhesive (PSA) development. A six-reaction transesterification model was calibrated against published data and used to select glycolysis conditions: 120 min at 220 °C and a PLA-repeat-unit:glycerol molar ratio of 1:0.25. Model–experiment discrepancies were 0.2% for hydroxyl value, 10.9% for apparent number-average molar mass, and 3.3% for apparent weight-average molar mass, indicating agreement with the calibration dataset. Oligomers were partially esterified with maleic anhydride (MA; nominal OH:MA ratios of 1:0.2–1:0.7) under ATR-FTIR monitoring and UV-cured at 365 nm with 10–40 wt.% 2-hydroxyethyl acrylate (HEA) on precursor mass. Tack and T-peel resistance increased with HEA loading, whereas apparent lap-shear strength showed precursor-dependent trends, including intermediate-loading maxima. A formulation with OH:MA = 1:0.5 and 30 parts HEA combined an apparent lap-shear strength of 0.30 MPa, T-peel resistance of 0.20 N/mm, and loop-tack force of 9.6 N/25 mm. These findings support glycolysis-derived PLA oligomers as tunable, partially biobased, PSA precursors.

Polymers doi: 10.3390/polym18222830

Authors: Jiawang Gao Yonghui Zhao Quan Shi Lichen Shen Zepeng Wang

At matched interchain joining counts, sulfur-crosslinked solution-polymerized styrene–butadiene rubber (SSBR) exhibited tighter packing, lower molecular mobility and greater local stiffness than triallyl isocyanurate (TAIC)-crosslinked SSBR. Atomistic molecular dynamics and small-strain calculations compared three matched parent sequences, each with 30 interchain joining contributions per crosslinked cell, alongside uncrosslinked controls. The smaller sulfur cells yielded higher joining-count density. Relative to TAIC, sulfur reduced the geometric free-volume fraction (FFV) by 5.67–6.30 percentage points and rubber-atom mean-squared displacement (MSD) at 250 ps by 60.0–64.8%. Its Hill Young’s modulus was 2.24–2.86 times that of TAIC. Sulfur also retained higher cooling-density breakpoints under all nine common analysis rules. These results jointly connect the spatial concentration of joining contributions, free volume and molecular motion to differences in network constraints between the two formulations. Equal joining counts or higher node functionality did not confer equal or greater local stiffness. A joint assessment of connectivity, packing and motion identified the defining formulation characteristics: greater local stiffness and restricted motion in sulfur, versus more free space and mobility in TAIC.

Polymers doi: 10.3390/polym18222829

Authors: Mohamed F. Ayad Abdulhamaid A. Maghrabi

Marginal microleakage is a major concern in restorative dentistry and affects the longevity of dental restorations. This study evaluated whether fluorinated dental bonding resins could reduce microleakage in composite resins. Experimental light-cure bonding resins—both filled (F) and unfilled (U)—were created with a base resin (45% BIS-EMA, 40% TEGDMA, 15% HEMA). Fluorinated TEGDMA (f-TEGDMA) replaced TEGDMA at concentrations of 0–30 wt%. Class V restorations were performed on 50 extracted human molars at the cementoenamel junction. Eight experimental formulations and two commercial bonding resins (OptiBond Solo Plus and All-Bond 2) were tested (n = 5 each). After 1500 thermocycles between 5 °C and 55 °C, teeth were immersed in a 50% silver nitrate solution and sectioned, and dye penetration at the occlusal and cervical margins was measured under magnification. Data were analyzed using analysis of variance and a post hoc test (α < 0.05). Incorporating f-TEGDMA into bonding resins did not significantly reduce microleakage at either margin. At occlusal margins, OptiBond Solo Plus and non-fluorinated filled resins exhibited significantly less leakage than fluorinated experimental resins. At cervical margins, commercial resins and fluorinated experimental resins demonstrated comparable penetration. These findings reinforce the challenges of achieving durable tooth-restoration interfaces and emphasize the ongoing need for improved bonding systems in restorative dentistry.

Polymers doi: 10.3390/polym18222828

Authors: Chenguang Li Zhanyang Lin Mingrui Du Xupei Yao Shiming Liu Shiao Chen Haijian Su Liang Chen Yanke Shi

Invert voids beneath underground concrete pipelines can cause support loss and settlement, while the spatial evolution of interfacial forces generated by confined polymer foaming remains poorly understood. Small-scale curved-interface grouting tests were conducted to investigate the effects of grout density, interface arch height, and circumferential position on local expansion forces, and a quadratic response surface model was developed for force prediction. Full-scale pipeline lifting tests were subsequently performed to investigate the relationship between interfacial expansion and structural displacement. The expansion response exhibited three stages—filling, rapid foaming, and stabilization—with pronounced spatial nonuniformity. Increasing grout density from 0.26 to 0.36 g/cm3 increased the peak expansion force by 58.9–69.7%, whereas increasing arch height from 8.14 to 14.60 mm resulted in an increase of only 5.3–9.2%. The response surface model showed good agreement with the experimental data used for model development (R2 = 0.9896). The full-scale test achieved a pipeline uplift of 50 mm, with the bell section lifting approximately 2.1 times faster than the spigot section during rapid uplift. A simplified equilibrium analysis yielded a theoretical critical grout density of 0.29 g/cm3 for initiating pipe uplift providing a preliminary reference for grouting parameter design and pipeline rehabilitation.

Polymers doi: 10.3390/polym18222827

Authors: Salman A. Alshamrani

Polymer-modified cementitious mortars are widely used to repair concrete. However, favorable properties of isolated mortar specimens do not guarantee durable bonded repairs. This critical review examines how polymer chemistry and delivery form, hydration and film formation, substrate condition, dimensional and electrochemical compatibility, and exposure history jointly control repair performance. Foundational studies are combined with recent work on waterborne epoxy, functionalized acrylate, redispersible powder, and in situ polymerization systems. The reviewed evidence supports formulation-specific benefits, but it does not support a universal optimum polymer content or a general ranking of polymer families, because studies differ in dosage definitions, curing histories, bond-test stress states, and failure-mode reporting. Within-study data show these trade-offs. In one mixture series, 10% SBR reduced water absorption by 75% but compressive strength by 49%. Under sustained loading with seawater wet–dry cycling, a waterborne-epoxy-modified interface lost 30% of its initial tensile bond, compared with 50% for the reference. A four-gate qualification framework linking placement, initial adhesion, retained performance under restraint and exposure, and field robustness is proposed together with a minimum reporting dataset. Thus, repair selection should be based on the performance of the complete repair–substrate system rather than on compressive strength or polymer dosage alone.

Polymers doi: 10.3390/polym18222826

Authors: Honggang Chen Yangyang Xu Xueru Luo Weichao Wang Jun Lin Shaojian He Kaiqing Li

Prolonged ultraviolet (UV) exposure degrades the mechanical, hydrophobic, and dielectric performance of silicone rubber (SIR) used in outdoor high-voltage insulation. Here, montmorillonite (MMT) was sequentially treated with polydopamine (PDA) and vinyltrimethoxysilane (VTMS) and incorporated into SIR at 0.5–5 phr (parts per hundred rubber). Spectroscopic and thermal analyses indicated changes in the MMT surface chemistry after treatment, and the composites were evaluated before and after 500 and 1000 h of accelerated UV aging. Among the 2 phr formulations selected for detailed comparison, SIR/2 VTMS-PDA@MMT exhibited favorable aging-property retention: after 1000 h, its tensile-strength retention was 103.2% and its elongation at break was 158%, compared with 57.7% tensile-strength retention for reference SIR. Its breakdown-strength retention was 94.6%, compared with 83.5% for SIR, and its static water contact-angle retention was 95.1%, compared with 77.8% for SIR, with comparatively small aging-induced changes in hardness and fracture morphology. The comparative results show that the MMT surface treatment and filler formulation influence the retention of mechanical, dielectric, and surface properties during accelerated UV exposure, providing guidance for the design of UV-resistant SIR composites.

Polymers doi: 10.3390/polym18222824

Authors: Tongtong Cao Hao Du Yuyun Yang Yuhua Cao

A facile strategy for fabricating bicontinuous emulsions stabilized by an amphiphilic random copolymer, poly(hexyl methacrylate-co-methacrylic acid) (P(HMA-co-MAA)), was developed. The copolymer in aqueous solutions with pH less than 9.0 could self-assemble to form aggregates, whose morphologies were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The wettability of the self-assembly aggregates at the oil–water interface was investigated through three-phase contact angle measurements, which demonstrated a clear pH-responsive transition. As pH decreased, the contact angle gradually increased. At pH 7.0 and 8.0, the contact angle approached 90°. Based on this property, the bicontinuous emulsions were successfully prepared by a direct mixing method utilizing caprylic/capric triglyceride (GTCC) as oil phase and 1.0% (w/v) P(HMA-co-MAA) aqueous solution with pH 7.0 and 8.0 as the aqueous phase. Furthermore, the effects of oil–water mass ratio, polymer concentration, and copolymer monomer ratio on the formation of bicontinuous emulsions were also systematically studied. The findings revealed that only the copolymer with the monomer ratio of 7:3 had the same wettability in both oil and aqueous phases at pH 7.0 and 8.0. These copolymer aggregates could rapidly adsorb at the interface and produce a “soft jamming” effect, thereby effectively inhibiting phase separation.

Polymers doi: 10.3390/polym18222825

Authors: Muhammad Tahir Dominik Steineder Rafael E. Hincapie Torsten Clemens Amir Farzaneh Silvan Mikulic Johannes Schnöller

Alkali–polymer (AP) flooding is a complex enhanced oil recovery (EOR) technique whose performance depends on reservoir mineralogy, crude oil properties, and formation water chemistry. The interactions among these factors can result in inconsistent field performance and make reliable prediction of AP breakthrough a key challenge for commercial applications. Accurate identification of breakthrough is particularly important because it directly influences operational decisions, including inhibitor dosing and production optimization. This study investigates the limitations of using pH as a standalone breakthrough indicator and proposes a multi-parameter analytical approach incorporating divalent cation concentrations, polymer concentration, alkalinity, and ammonia generation. As part of an Austrian AP flooding pilot project, laboratory core-flooding experiments were conducted under representative reservoir conditions. Two-phase flooding experiments were performed using 30-cm-long crude-oil-saturated core samples. The cores were sequentially injected with polymer and AP solutions to simulate field operations. Effluent samples were analyzed for iodide tracer concentration, sodium, calcium, magnesium, pH, alkalinity, ammonia, and polymer concentration. To evaluate the reproducibility of the results, duplicate experiments were conducted. In addition, a third experiment without polymer pre-flushing was performed to isolate AP breakthrough behavior. Field production data were subsequently analyzed to validate the laboratory observations. The results demonstrate that pH alone is insufficient for reliable assessment of AP breakthrough. Polymer concentrations in the effluent reached up to 1.9 times the injected concentration following AP injection into polymer-preconditioned cores, suggesting release of polymer retained during the preceding polymer flood. Alkali-induced desorption is considered a plausible mechanism; however, the present experiments do not independently distinguish desorption from other retention-release mechanisms. The laboratory experiments showed reproducible analytical response sequences, with Ca2+ decline preceding the main pH response under the investigated conditions. Comparison with selected pilot data showed qualitative consistency in the relative sequence of the principal indicators, although absolute timing differed between laboratory and field scales. The results support a multi-parameter framework for interpreting AP breakthrough while highlighting the limitations of using pH as a standalone indicator.

Polymers doi: 10.3390/polym18222823

Authors: Mohamed F. Ayad Abdulhamaid A. Maghrabi

The bond strength of adhesive resins to tooth structure is a key factor in restoration longevity. This study assessed the impact of substituting TEGDMA with fluorinated TEGDMA (f-TEGDMA) on the shear bond strength of experimental adhesive resins to enamel and dentin. Eight experimental light-cured resins (45 wt% Bis-EMA, 40 wt% TEGDMA/f-TEGDMA, 15 wt% HEMA) were prepared, both filled and unfilled, with f-TEGDMA at 0%, 17%, 24%, and 30 wt% of the monomer base. These were compared to OptiBond Solo Plus (filled) and All-Bond 2 (unfilled). Composite cylinders were bonded to etched enamel and dentin of human molars, stored for 24 h at 37 °C, and tested for shear bond strength. Data were analyzed using one-way ANOVA and Tukey’s test (α = 0.05). Bond strength varied significantly among groups for both substrates (p < 0.001). For enamel, the filled resin without f-TEGDMA matched OptiBond Solo Plus, while any f-TEGDMA concentration reduced filled-resin bond strength (p ≤ 0.013). Unfilled resins were unaffected by f-TEGDMA and were comparable to All-Bond 2. For dentin, only the unfilled resin without f-TEGDMA matched OptiBond Solo Plus; all f-TEGDMA-containing resins were comparable to All-Bond 2 and significantly lower than OptiBond Solo Plus (p < 0.001). f-TEGDMA did not enhance bond strength to either substrate. Dentin bonding was more sensitive to resin composition than enamel bonding.

Polymers doi: 10.3390/polym18222822

Authors: Xin Jin Zhixing Pan Yanhai Yang Ye Yang Hongbin Zhu Jiupeng Zhang

To promote high-value utilization of reclaimed asphalt pavement (RAP), this study developed 100% RAP warm-mix recycled asphalt mixtures using a laboratory-synthesized polymer-based warm-mix rejuvenator. The AC-13 gradation was reconstructed through RAP fractionation and recombination, followed by screening and selection of the RAP preheating temperature, mixing temperature, and rejuvenator dosage within the investigated experimental ranges. The selected mixture, prepared at 120 °C preheating, 145 °C mixing, and 2.5‰ rejuvenator by RAP mass, satisfied the investigated laboratory criteria for high-temperature stability, low-temperature cracking resistance, and freeze–thaw moisture stability. Uniaxial cyclic compression tests showed that cyclic compressive failure life decreased with increasing stress ratio and loading frequency, whereas temperature exerted a nonmonotonic effect, with the highest life among the three tested temperatures occurring at 15 °C. Three-way ANOVA identified stress ratio, loading frequency, and temperature as significant factors (p < 0.001), accounting for 64.61%, 24.05%, and 8.97% of the total variance within the investigated factor ranges, respectively. FTIR showed relative changes in oxidation-related spectral indices after rejuvenator addition, while μCT provided complementary characterization of CT-resolvable porosity and void topology. These results demonstrate the laboratory feasibility of the investigated 100% RAP warm-mix recycled mixture and characterize its cyclic compressive response and multiscale structural features without implying a direct causal mechanism.

Polymers doi: 10.3390/polym18222821

Authors: Şahin Özel Aslı Göçenoğlu Sarıkaya

Magnetic polymeric hybrid microspheres based on poly(vinylphenylboronic acid-co-divinylbenzene), Fe3O4, and TiO2 [P(VBA-co-DVB)/Fe3O4-TiO2] were synthesized and investigated as adsorbent supports for laccase immobilization. The physicochemical, morphological, structural, and surface characteristics of the microspheres were evaluated by SEM, FT-IR, BET, XRD, and zeta potential analyses. The resulting polymeric hybrid microspheres exhibited a porous polymeric architecture, magnetic responsiveness, and functional surface groups capable of promoting enzyme–support interactions. A BET surface area of 50.26 m2 g−1 was obtained, with BJH average pore diameters of 16.53 and 36.11 nm for the adsorption and desorption branches, respectively. Laccase was directly immobilized from an ultrafiltered crude enzyme preparation without additional chromatographic purification or the use of an external cross-linking agent, predominantly through adsorption and multipoint non-covalent interactions. Approximately 79% of the initial soluble laccase activity was removed from the liquid phase during immobilization. The catalytic properties of free and immobilized laccase were comparatively evaluated in terms of pH-dependent activity, apparent kinetic parameters, thermal stability, storage stability, and operational reusability. Immobilization altered the apparent kinetic response of the enzyme, improved activity retention during storage, and provided partial, temperature-dependent protection against thermal inactivation. In addition, the magnetic nature of the polymeric hybrid microspheres enabled rapid recovery and repeated use of the immobilized biocatalyst, which retained 43% of its initial activity after 20 catalytic cycles. These findings demonstrate that the developed magnetic polymeric hybrid microspheres provide a recoverable and reusable platform for direct laccase immobilization from ultrafiltered crude preparations and may offer advantages for simplified enzyme processing, reusable biocatalysis, and environmental applications.

Polymers doi: 10.3390/polym18222820

Authors: Ramil Akhundov Baris Baser

This in vitro study evaluated the effects of printing orientation and post-curing duration on the flexural strength, Vickers microhardness, and surface roughness of standardized specimens fabricated from a nanoceramic hybrid resin intended for fixed lingual retainer applications. A total of 144 specimens were fabricated using a SprintRay Pro S DLP printer and SprintRay OnX Tough 2 resin and allocated to nine experimental groups according to printing orientation (0°, 45°, and 90°) and post-curing duration (1, 10, and 20 min). Of the 16 specimens fabricated per group, eight were allocated to flexural strength testing, while the remaining eight were used for both Vickers microhardness and surface roughness measurements. Flexural strength was assessed via three-point bending, microhardness via the Vickers test, and surface roughness via profilometry. Normally distributed outcomes were analyzed using a two-factor factorial model, whereas non-normally distributed outcomes were analyzed using robust ANOVA, with statistical significance set at p < 0.05. Both printing orientation and post-curing duration significantly affected flexural strength (p < 0.001 and p = 0.026, respectively), with a significant interaction (p < 0.001); the highest mean flexural strength was recorded at 45° with 20 min of post-curing (144.24 MPa), closely followed by 90° with 10 min (144.12 MPa). Microhardness was significantly affected by both factors (p < 0.001), with no statistically significant interaction (p = 0.245); the highest mean microhardness was observed at 0° with 20 min of post-curing. Surface roughness was significantly influenced by printing orientation only (p = 0.030), being highest at 90°. The effects of printing orientation and post-curing duration varied across the investigated properties, with a significant interaction observed for flexural strength. These findings provide material-level evidence regarding the influence of manufacturing parameters on OnX Tough 2 resin but do not establish optimal processing conditions for the clinical performance of fixed lingual retainers.

Polymers doi: 10.3390/polym18222819

Authors: Joseph Kesserwani Sami Youssef Anna Maria ElBayssari Chawki Lahoud

Lattice-core sandwich structures made of carbon fibre-reinforced polymer (CFRP) are attractive for lightweight aerospace and naval structures, but their epoxy matrix softens near its glass transition temperature (Tg). This study predicts the stiffness and failure of CFRP sandwich beams with a body- and face-centred Z-strut (BFCZ) lattice core at elevated temperature and under one-sided heat flux, using a three-dimensional finite element (FE) model coupled to a verified unit-cell thermal model. Validation was possible only for pyramidal cores: against published bending tests at 20–200 °C, the FE model, calibrated once at 20 °C, reproduced the stiffness to within 10% and, using node strengths from independent shear tests, the failure load to within 13% up to 180 °C. The BFCZ results are therefore predictions that require experimental verification. At equal strut diameter, the BFCZ beam is predicted to be 1.85 times stiffer and 2.05 times stronger than the pyramidal beam, but it contains 4.6 times more strut material; at equal mass or equal core density (2–15%), the pyramidal core is predicted to be at least as stiff and at least as strong. Under heat fluxes of 2.5–10 kW·m−2, the exposed face reaches 90% of its steady temperature rise within 2.5–5 min, when most of the stiffness and strength is lost; assuming uniform heating to the exposed-face temperature underestimates the residual stiffness by about 28% at 5 kW·m−2.

Polymers doi: 10.3390/polym18222818

Authors: Wenhao Lin Tingfu Li Xiaoxiao Zheng Guocai Zheng Jipeng Chen Fengcai Lin Weibin Bai Jianrong Xia Qi Lin Yanlian Xu Donghui Wang

Conventional self-polishing antifouling coatings rely heavily on petroleum-based polymers and hydrodynamic shear force, rendering them ineffective for stationary marine infrastructure while raising environmental concerns. Natural urushiol offers a promising bio-based alternative, yet its hyper-reactive conjugated side chains lead to uncontrollable auto-oxidation and severe storage failure—creating a sharp paradox between non-intended self-curing and target-controlled degradation. Herein, we report a sustainable, hydrolysis-driven static self-polishing polyurethane (PU) coating that resolves this fundamental dilemma. By stabilizing the volatile urushiol framework and integrating hydrolytically degradable poly(ε-caprolactone) (PCL) soft segments, the resulting PU architecture completely overcomes structural instability while achieving tailored microphase separation. This optimized molecular network grants the coating excellent thermal stability, strong substrate adhesion, high impact resistance, and superior flexibility. Crucially, controlled hydrolysis of the PCL backbones drives uniform, layer-by-layer surface renewal under static seawater conditions without requiring shear flow. The erosion kinetics can be further fine-tuned across a broad dynamic range by incorporating natural rosin. Driven by this continuous self-renewing interface, the coating exhibits exceptional broad-spectrum resistance against representative marine biofouling, achieving anti-adhesion efficiencies of 87.83% against Bacillus sp. and up to 99.41% against Nitzschia closterium. This work provides a sustainable natural molecular design strategy for bio-based static self-polishing coatings.

Polymers doi: 10.3390/polym18222817

Authors: Mashan Almutairi Ahmed Adel Ali Youssef Gehad M. Subaiea Ahmed Alobaida Alia Alshammari

Levofloxacin (LFX) is widely prescribed to treat bacterial ocular infections. However, its topical application as eyedrops faces rapid precorneal clearance and poor ocular surface residence. These limitations often require frequent administration. In this project, ocular inserts loaded with LFX were developed using hot-melt extrusion (HME) to address these shortcomings. A D-optimal mixture design was applied to study the effects of hydroxypropyl cellulose (HPC-JXF), polyethylene oxide (PEO-N10), and sorbitol on LFX-release behavior. Sixteen insert formulations were prepared and evaluated for their physicochemical characteristics and in vitro dissolution performance. All developed inserts showed adequate weight uniformity, thickness, surface pH, and drug content. Statistical analysis results revealed that formulation composition had a marked influence on LFX release at both 0.5 and 8 h time points. PEO-N10 played a key role in improving LFX release; however, HPC-JXF contributed to release retardation and preservation of matrix integrity. Numerical optimization identified a formulation containing 90% polymer content of HPC-JXF and 10% LFX as the optimal extended-release system. The optimized formulation released ~18% of LFX within the first 30 min and ~64% at 8 h, indicating close agreement between the experimental results and model-predicted values. Differential Scanning Calorimetry thermograms suggested that HME processing helped in the molecular dispersion of LFX throughout the polymeric carrier, resulting in an amorphous drug distribution within the insert matrix. The Korsmeyer–Peppas release exponent, determined via DDSolver modeling, indicated anomalous transport, where drug diffusion and polymer relaxation contributed to the release process. Overall, the project outcomes prove the potential of HME for the fabrication of LFX-loaded ocular inserts with tunable release characteristics that range from immediate to extended release. The optimized insert formulation could be a promising alternative platform to conventional ophthalmic eyedrops for the management of bacterial ocular infections.

Polymers doi: 10.3390/polym18222816

Authors: Julijana Žeravica Olga Govedarica Mirjana Jovičić Sonja Stojanov Dragan Govedarica

Although epoxidized and conventional vegetable oils are increasingly being considered as sustainable processing aids for natural rubber (NR) compounds, the relationships between their physicochemical characteristics, vulcanization behavior, and vulcanizate performance remain insufficiently understood. This study investigated the effects of epoxidized soybean oil and six conventional vegetable oils at oil loadings of 10, 20, and 30 phr. Physicochemical characteristics, mixing power consumption, rheometric parameters, and selected mechanical properties were evaluated. Principal component analysis (PCA) and Pearson correlation analysis were used to examine associations within the dataset, while artificial neural network models were developed for tensile strength (TS), stress at 300% elongation (M300), and maximum torque (Mmax). The first three principal components explained 89.74% of the total variance. Oil loading, rheometric torque parameters, viscosity, surface tension, and iodine number were strongly associated with variation in the investigated compound properties. Within the original random data split, the selected ANN models reproduced a substantial proportion of the variation in the modeled responses. Sensitivity analysis indicated that the calculated M300 and Mmax responses were most strongly dependent on oil loading, whereas the calculated TS response showed the greatest dependence on mixing power consumption and oil loading. However, leave-one-oil-out grouped validation yielded negative pooled R2 values for all three responses, indicating limited generalization to oil types excluded from model development. The PCA, correlation, and ANN results should therefore be interpreted as exploratory descriptions of relationships within the investigated oils and loading range rather than as evidence of causal mechanisms, externally validated predictive performance, or demonstrated applicability to formulation optimization.

Polymers doi: 10.3390/polym18222815

Authors: Wonjun Kang Daeseong Yong Jaeup U. Kim

Conformationally asymmetric diblock copolymer melts exhibit close competition between conventional body-centered-cubic (BCC) and face-centered-cubic (FCC) sphere packings and more complex Frank–Kasper phases near the order–disorder transition (ODT). How compositional fluctuations reshape this competition remains poorly understood. We use Langevin field-theoretic simulation (L-FTS), with discrete-chain self-consistent field theory (SCFT) as a mean-field reference, to obtain ODT estimates and examine nearby morphological transformations among BCC, FCC, and four Frank–Kasper phases (σ, A15, C14, and C15). In monodisperse melts at an invariant polymerization index of N¯=105, where fluctuations are relatively weak, the estimated transition thresholds remain closely spaced, consistent with small SCFT free-energy differences per chain. At N¯=104, stronger fluctuations increase the separation between BCC disordering and Frank–Kasper transformation thresholds. BCC remains ordered at lower segregation strengths, and several Frank–Kasper initial states transform into BCC-like packings before disordering. In disperse systems modeled by binary blends at N¯=104, increasing chain-length dispersity narrows the separations between BCC and Frank–Kasper thresholds. Nevertheless, BCC remains ordered at lower segregation strengths than other initial morphologies, even at higher dispersity where SCFT favors FCC. These results suggest that compositional fluctuations and chain-length dispersity affect spherical morphologies differently near the ODT.

Polymers doi: 10.3390/polym18222814

Authors: Mónica P. S. Ferreira Luisa M. Arruda José Sousa Duarte Dias João Bessa Luís Oliveira Helder Carvalho Raul Fangueiro

This study investigates the interplay between carbon nanofiller morphology and functionalisation methods in textile piezoresistive sensors. We compare two distinct functionalisation strategies (knife coating and foulard impregnation) for incorporating graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) into polyester knits. Thermal and structural analyses confirmed that both methods preserve nanofiller integrity, though impregnation better maintains the fabric’s native thermal stability by avoiding the formation of continuous surface films. Electrical analysis revealed that the two-dimensional GNPs required the continuous film of knife coating to percolate, whereas the one-dimensional CNTs are inferred to physically entangle to establish effective conductive pathways in both methods. However, it was the resulting structural architectures that influenced the final piezoresistive performance. The best-performing knife-coated GNP formulation (5 wt.%) achieved a low-force sensitivity of S2–20N = 0.032 N−1 but exhibited dynamic instability under cyclic compression (maximum coefficient of variation, CV ~28%), likely due to poor mechanical interlocking. Impregnation preserved the knit’s porosity and seems to have shifted the sensing mechanism to inter-yarn contact resistance, an advantage CNTs could leverage. The best-performing impregnated 2 wt.% CNT formulation combined high cyclic dynamic stability (CV < 10%) with broad-range sensitivity across low-force (S2–20N = 0.027 N−1) and high-force (S20–80N = 0.0024 N−1) regimes. This piezoresistive response and dynamic signal stability suggested a behaviour comparable to the commercial Velostat benchmark, highlighting the potential of this scalable fabrication route for wearable piezoresistive sensors.

Polymers doi: 10.3390/polym18222813

Authors: Raigul Zh. Jumanova Gulmira S. Beisenova Gulzhan L. Badavamova Gulnarkhan Kurmangazhy Amanbol Alipbayev Salamat S. Yegeubayeva

Bentonite-based carriers can be used to control the release of natural corrosion inhibitors. In this study, sodium-activated bentonite was used to load tannin and was subsequently modified with chitosan to regulate tannin release. The effects of contact time and initial pH on tannin loading were investigated using UV-Vis spectrophotometry. The highest adsorption capacity (56.98 ± 0.72 mg g−1) was obtained at an initial pH of 4.5 and a contact time of 12 h. The prepared materials were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). FTIR results showed changes in the hydroxyl and silicate regions after modification. XRD analysis showed small changes in the basal spacing from 14.42 Å for Bent to 14.88 Å for Bent@Tan and 14.60 Å for Bent@Tan@Chit, indicating that the layered structure was largely preserved. TGA showed an increase in mass loss between 200 and 450 °C from 1.42% for Bent to 2.25% for Bent@Tan and 6.68% for Bent@Tan@Chit, consistent with the presence of additional organic components. Tannin release was investigated in 3.5 wt.% NaCl solution at an initial pH of 5.0 over 48 h. Bent@Tan showed rapid initial release, while Bent@Tan@Chit showed lower early release followed by a gradual increase. Kinetic analysis showed the highest goodness of fit for the first-order model for Bent@Tan (R2 = 0.816) and the zero-order model for Bent@Tan@Chit (R2 = 0.968). These results demonstrate differences in the apparent tannin release profiles of Bent@Tan and Bent@Tan@Chit. The prepared composite may be considered for future studies of anticorrosion coatings; however, its corrosion-inhibiting performance has not yet been experimentally evaluated.

Polymers doi: 10.3390/polym18222812

Authors: Joaquín Ródenas-Rochina Luis Amaro Martins Diana C. Akudolu-Imafidon Roser Sabater i Serra José Antonio Gómez-Tejedor Senentxu Lanceros-Méndez José Luis Gómez Ribelles Isabel Tort-Ausina

Significant amounts of antibiotics are found in wastewater and drinking water streams due to their widespread use in human and veterinary medicine and their incomplete uptake by living organisms. Among the technologies developed to address this problem, adsorption and advanced oxidation processes, including photocatalysis, are widely employed for the remediation of antibiotic-contaminated waters. In this work, poly(vinylidene fluoride) (PVDF)/TiO2 composite microspheres with highly porous structures were developed and evaluated for the removal of ciprofloxacin (CIP) from aqueous solutions. Scanning electron microscopy revealed that TiO2 nanoparticles migrate towards the microsphere surface during PVDF crystallisation, forming a dense surface coating, whereas the microsphere interior remains highly porous. Focused ion beam microscopy confirmed the presence of TiO2 within the inter-spherulitic regions of the microsphere core. A key finding is that a pre-wetting protocol facilitates water penetration into the highly hydrophobic PVDF structure, enabling efficient CIP adsorption in the dark, while untreated microspheres show only limited adsorption. This work demonstrates that CIP removal by porous PVDF/TiO2 microspheres is associated with both the surface segregation of TiO2 nanoparticles and the accessibility of the porous structure to water. These findings emphasise the importance of pore accessibility in the design of porous polymer-based materials for water treatment.

Polymers doi: 10.3390/polym18222811

Authors: Eman M. Elkady Fahad M. Alminderej Mahmoud Mahrous M. Abbas Safaa R. Fouda

Pharmaceutical antibiotics in aquatic systems have led to a need for effective, re-usable and highly structurally stable materials for contaminant removal purposes. In this study, hybrid nanocomposites based on multifunctional nanocomposites with NiWO4 and La-doped ZnFe2O4 loaded in the matrix of montmorillonite/PMMA/CMS modified with Jeffamine-D400 were prepared and investigated for removal of amoxicillin (AMX) from water solution. The formation of heterogeneous structures was confirmed by FTIR, XRD, SEM–EDX, TEM and zeta potential techniques. There was an increase in the basal spacing of MMT from 6.9 Å for D400-MMT to 9.3–9.4 Å after the incorporation of the polymeric and inorganic phases. The adsorption efficiency was in the order S3 (La-doped ZnFe2O4/NiWO4@PMMA/CMS@D400-MMT) > S2 (NiWO4@PMMA/CMS@D400-MMT) > S1 (PMMA/CMS@D400-MMT). The adsorption efficiency of S3 was about 98% at pH 5. The kinetic study revealed that AMX adsorption on the material was influenced by several mechanisms of surface adsorption, mass transfer through the boundary layer, and intraparticle diffusion. At the initial concentration of AMX of 300 mg L−1, the experimentally obtained equilibrium adsorption capacities of S1, S2, and S3 were about 250, 265, and 290 mg g−1, respectively. The nonlinear isotherm analysis revealed that the adsorption data can be described more precisely using the Langmuir model. The maximum adsorption capacities obtained from the isotherms according to the Langmuir model were 278.12, 295.73, and 323.17 mg g−1 for S1, S2, and S3, respectively, while a lesser correlation coefficient was obtained for the Freundlich model. The increasing adsorption capacity obtained from the Langmuir isotherm from S1 to S3 confirms the beneficial effect of NiWO4 and La-doped ZnFe2O4 on the adsorption ability of the composite. Five repeated adsorption–regeneration cycles showed that after five adsorption cycles, S3 retained about 82% of its initial adsorption capacity.

Polymers doi: 10.3390/polym18222808

Authors: Anna Fajdek-Bieda Agnieszka Wróblewska

The journal retracts the review article “The Use of Natural Minerals as Reinforcements in Mineral-Reinforced Polymers: A Review of Current Developments and Prospects” [...]

Polymers doi: 10.3390/polym18222810

Authors: Damián Peti Gabriel Stolárik Róbert Ropovik Radoslav Vandžura

Material extrusion (MEX) components remain limited by incomplete inter-road bonding and process-induced voids, which govern both load transfer and final fracture. This study investigated whether vacuum pretreatment can intensify the effect of short-term hydrothermal annealing on the tensile response and fracture characteristics of MEX-manufactured PLA. Ninety treated specimens were distributed among 30 treatment cells, comprising 15 temperature–time combinations for each pretreatment condition, with three specimens processed simultaneously within each treatment cell. Hydrothermal annealing was performed at 50–90 °C for 1–3 min. Fracture morphology was examined by digital optical microscopy and scanning electron microscopy (SEM). Tensile properties were evaluated according to ISO 527 and analyzed using general linear models (GLMs) with Tukey-adjusted comparisons. Vacuum pretreatment increased the estimated marginal mean maximum tensile stress from 61.8 MPa to 67.3 MPa (+5.53 MPa; 95% CI: 4.19–6.86 MPa; p < 0.001) and elongation at maximum load from 3.95 mm to 4.38 mm (+0.426 mm; 95% CI: 0.332–0.519 mm; p < 0.001). Temperature significantly affected maximum tensile stress (p = 0.002) and elongation (p = 0.001), with significant processing-route-by-temperature interactions for both responses (p = 0.014 and p = 0.027, respectively). Annealing time affected neither response significantly, while stress at break was not significantly affected by processing route (p = 0.194). Fractography revealed persistent inter-road voids and mixed interfacial–cohesive failure. Vacuum-pretreated specimens exhibited more compact central fracture regions and altered crack localization, although process-induced voids remained preferential sites of final failure. The results demonstrate that vacuum pretreatment was primarily associated with load transfer and deformation before maximum loading, whereas resistance to final fracture remains controlled by defects.

Polymers doi: 10.3390/polym18222809

Authors: Jianfeng Wang Peida Yang Yang Zhao Tianxiang Ren Na Li Ping Jiang Haihua Zhan Yonghui Zhang

Virgin and recycled polypropylene fibers (PPF and rPPF) can reinforce cement-based materials, but their surface inertness limits interfacial bonding. This review examines ultraviolet (UV)-induced surface modification, linking changes in surface chemistry, morphology and wettability with fiber integrity, interfacial behavior and composite performance. UV-induced photo-oxidation introduces polar functional groups and modifies surface morphology, potentially improving fiber–matrix compatibility and mechanical performance. However, these benefits depend on irradiation conditions, fiber characteristics and matrix composition. In one cement-paste study using 2 vol.% PPF, UV treatment increased 28-day compressive strength at room temperature by 24% and residual compressive strength after exposure to 200 °C by 18%, relative to specimens containing the same dosage of untreated PPF. For rPPF, pre-existing oxidation and recycling-related variability require treatment conditions tailored to its initial state. Excessive irradiation may degrade fiber properties, highlighting the need to balance surface functionalization with mechanical integrity. Limited mechanistic evidence, long-term performance data and standardized protocols remain key challenges. This review identifies the potential and limitations of UV modification and outlines research needs for its application to virgin and recycled polypropylene fibers in cement-based materials.

Polymers doi: 10.3390/polym18222807

Authors: Qing Qu Xin Zheng Dan Tan Kailiang Ren

Flexoelectricity-enhanced photovoltaic (FPV) effect has emerged as one of the significant research interests. In this investigation, we found it for the first time that the bandgap modulation effect played a critical role on the FPV effect of poly (vinylidene fluoride) (PVDF)-based polymer films. By using the ultraviolet-visible- near Infrared (UV-Vis-NIR) absorption spectra, we demonstrated that bending strain results in pronounced and reversible bandgap modulation. Specifically, concave bending (compression strain, ITO electrode on top of PVDF film) results in −86 meV bandgap narrowing in the PVDF (28 µm) film, whereas convex bending (tensile strain) causes bandgap widening of +97 meV. For polarized PVDF films, the samples showed comparable shifts of −88 meV and +114 meV under concave bending and convex bending conditions, respectively. The observed behavior is attributed to dipole reorientation and changes in interchain electronic coupling induced by mechanical deformation. These findings provide new insights into strain–electronic coupling mechanisms in ferroelectric polymers and highlight the potential of these materials for strain-tunable flexible electronic and optoelectronic applications.

Polymers doi: 10.3390/polym18222806

Authors: Tatjana Antonić Jelić Lidija Androš Dubraja Dalibor Merunka Miroslava Lukešová Fraser John MacMillan Marin Tota Srećko Valić

This study investigates the influence of polydimethylsiloxane (PDMS) molecular weight on crystallization kinetics and molecular dynamics in pristine PDMS and PDMS–zeolite composites. Three PDMS samples with molecular weights of 4,000, 28,000, and 63,000 were examined. Zeolite A with spherical particle morphology was used as a filler, and composites containing 30 wt% zeolite were prepared. Crystallization kinetics and thermal behavior were investigated by differential scanning calorimetry (DSC), while changes in the local molecular dynamics of the amorphous phase during isothermal crystallization at −85 °C were monitored by electron spin resonance (ESR) using the spin probe method. Both DSC and ESR results demonstrate that the presence of zeolite accelerates isothermal crystallization, regardless of PDMS molecular weight, with the most pronounced effect observed for the intermediate molecular weight (28,000). Avrami analysis further confirms the strong influence of molecular weight on crystallization kinetics, with higher molecular weight PDMS crystallizing more rapidly in both pristine and zeolite-filled systems. The close correspondence between the characteristic times determined by DSC and ESR indicates a strong relationship between crystal formation and changes in the molecular dynamics of the remaining amorphous phase. Subsequent DSC heating scans revealed differences in melting behavior, with strongly overlapping melting endotherms for pristine low molecular weight PDMS and the corresponding zeolite composite, and clearly resolved double melting peaks for the higher molecular weight samples, suggesting differences in the stability and organization of the crystalline regions.

Polymers doi: 10.3390/polym18222805

Authors: Liudmila B. Maksaeva Maxim A. Petrunin Alevtina A. Rybkina Maria A. Agievich Angela A. Gribankova Denis I. Kuznetsov

The comparative corrosion resistance of additively manufactured and cast Al–Mg–Sc alloy 1575 remains uncertain because assessment methods and exposure durations yield conflicting results. This study examined fabrication method and organosilicon surface modification effects in 0.6 M NaCl, approximating seawater chloride concentration. Selective laser-melted and cast specimens were investigated by corrosion potential measurements, anodic polarization, electrochemical impedance spectroscopy, scanning reflectometry, gravimetry, profilometry, and optical microscopy. Protective vinyl- and aminosilane-derived layers and their mixtures were evaluated. The additively manufactured alloy showed a pitting potential of −0.400 V, 84 mV more positive than the cast alloy, indicating greater resistance to pitting initiation. A vinyl–aminosiloxane layer increased pitting potentials by 171 and 162 mV, respectively. However, impedance and long-term corrosion tests indicated greater overall corrosion resistance of the cast alloy. Additively manufactured specimens developed pits, whereas cast specimens underwent selective and quasi-uniform dissolution. Organosilicon layers reduced corrosion in both materials, depending on surface condition and degradation mechanism. Neither fabrication method was consistently superior: corrosion rankings depended on exposure duration, assessment method, and corrosion mechanism.

Polymers doi: 10.3390/polym18222804

Authors: Felix Baumgärtner Nils Huber Christian Bonten

This work presents a time-dependent pressure–specific volume–temperature (pvT) model for semi-crystalline thermoplastics under rapid cooling, crucial for understanding material behavior during manufacturing. The individual model components were evaluated against experimental pvT and calorimetric data, while the coupled model was used to predict the specific-volume evolution under rapid cooling conditions. The focus was on establishing an accessible procedure for determining material parameters, independent of geometry or process, through an inductive approach. A time-dependent description of the plastic’s pvT behavior was achieved by considering equilibrium states affected by pressure and temperature changes. The modeling incorporated temperature, pressure, and time dependence, alongside crystallization kinetics. The Dual Nakamura model was calibrated using isothermal DSC- and FSC measurements at ambient pressure, while pressure dependence was introduced through the pressure-dependent equilibrium melting temperature derived from pvT measurements. The pressure-dependent pvT behavior was experimentally characterized between 100 and 500 bar, whereas the crystallization kinetics were determined at ambient pressure. In contrast to the classical Tait model, the proposed approach explicitly accounts for time-dependent crystallization and cooling history. The calibration workflow represents a basis for cooling-rate-dependent material descriptions in injection-molding simulations.

Polymers doi: 10.3390/polym18222803

Authors: Xueheng Fang Yunfu Ou Yunxiao Zhang Tingyang Wu Junjie Ding Juan Li Xiongwu Yang Dongsheng Mao He Li

Developing anti-icing composite coatings integrating superhydrophobic, electrothermal, and photothermal functionalities is critical for guaranteeing the safe operation of key equipment in extremely cold environments. Layer-by-layer structural design is capable of maximizing the performance of each functional layer and avoiding overall functional failure caused by interlayer delamination. Herein, a bilayer composite coating was fabricated with a bottom carbon nanotube film (CNTF) layer and a multifunctional top coating. The underlying CNTF layer acts as an electrothermal functional layer to deliver efficient Joule heating. The top coating is composed of modified E-51 epoxy resin (M-E-51) and hexadecyltrimethoxysilane (HDTMS)-grafted polydopamine (PDA)-coated carbon nanotubes (H-CNT@PDA), which functions as a photothermally active layer, constructs a three-dimensional micro–submicrometre hierarchical superhydrophobic structure, and endows effective protection for the base CNTF layer. The prepared composite coating achieves synergistic electrothermal and photothermal de-icing performance: its surface temperature exceeds 100 °C at 3 V and reaches 52.0 °C under 0.9-sun irradiation, which is superior to the 47.4 °C achieved by pure CNTF. The coating also exhibits excellent superhydrophobicity with a water contact angle (WCA) of 156.1 ± 3.8° and a sliding angle (SA) of 6.2 ± 1.6°, along with a low ice adhesion strength of 60.1 kPa. De-icing tests verify that the coating can complete de-icing within 362 s under 1-sun illumination and 301 s under 3 V electric heating, demonstrating its outstanding dual electrothermal/photothermal de-icing capability for cold-condition anti-icing applications.

Polymers doi: 10.3390/polym18222802

Authors: Pervin Soyer A. Alper Öztürk

The development of multifunctional topical antiseptic formulations incorporating microbial-derived bioactive compounds represents a promising strategy for improving antimicrobial and antibiofilm performance. This study aimed to develop and comparatively evaluate chitosan- and Carbopol® 940-based antiseptic polymeric gels containing a Lactiplantibacillus plantarum-derived postbiotic. The postbiotic preparation was obtained through fermentation, cell removal, membrane filtration, and lyophilization and subsequently incorporated into polymeric gel formulations. The developed systems were characterized in terms of physicochemical and rheological properties, antimicrobial activity using agar well diffusion and minimum inhibitory concentration (MIC) assays, inhibitory effects on biofilm formation against Staphylococcus aureus and Pseudomonas aeruginosa, and antioxidant activity using the DPPH radical scavenging assay. Both formulations exhibited homogeneous appearances and shear-thinning behavior, supporting their potential suitability for topical application. The chitosan-based postbiotic formulation generally demonstrated superior antimicrobial performance, producing inhibition zones of up to 22.4 mm and achieving a two-fold reduction in MIC values compared with the non-formulated postbiotic. Concentration-dependent antibiofilm activity was observed, with the chitosan-based formulation achieving maximum biofilm inhibition of 62.5% against S. aureus and 59.3% against P. aeruginosa. Antioxidant evaluation further demonstrated enhanced radical scavenging activity following postbiotic incorporation, with the chitosan-based formulation reaching 72.0% DPPH inhibition and exhibiting the most favorable IC50 among the postbiotic-containing systems. The findings highlight the influence of polymeric matrix composition on the biological performance of postbiotic-containing polymeric gels and identify chitosan as a promising carrier for multifunctional topical antiseptic formulations. Further standardized antiseptic efficacy and safety studies are required to establish their practical applicability.

Polymers doi: 10.3390/polym18222801

Authors: Carlo De Luca Emmanuel De Gregorio Martina Butori Björn Eriksson Rakel W. Lindström Viviana Cigolotti Elio Jannelli Claudio Ferone Giuseppina Roviello Oreste Tarallo

Fluorine-free hydrocarbon proton-exchange membranes offer an alternative to perfluorosulfonic acid (PFSA) electrolytes, but good membrane-level properties do not always translate into membrane-electrode assembly (MEA) performance. Here, dense poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) films were sulfonated in the solid state, yielding a sulfur distribution that appeared homogeneous through the membrane thickness and ion-exchange capacities (IEC) of 1.17–2.20 meq g−1, corresponding to sulfonation degrees of 16–32 mol% and water uptake from 55 to 92%. The sulfonated PPO (sPPO) membrane with the highest IEC that remained self-standing was tested in a single-cell MEA and compared with a Nafion® 212-based MEA prepared and operated in the same way. The sPPO-based MEA showed lower hydrogen crossover and higher apparent short-circuit resistance than the Nafion® 212 reference. However, its high-frequency resistance (HFR) was also higher, corresponding to an apparent MEA-level conductivity of 11 mS cm−1 at 80 °C and 70% RH, compared with 40 mS cm−1 for Nafion® 212. This gap persists even though sPPO has a higher hydration number. Since the catalyst layers contain a PFSA ionomer, this HFR-based conductivity includes membrane, electrode, and interfacial contributions. The sPPO membrane reached a peak power density of 0.45 W cm−2 at 80 °C and 90% RH. In a short-term potentiostatic test, the sPPO-based MEA failed after approximately 6 h. Together with swelling, tensile, and Fenton data, these results identify dimensional control, oxidative stabilization, and better membrane–ionomer compatibility as the next steps and provide a quantitative MEA-level baseline for solid-state sulfonated PPO membranes.

Polymers doi: 10.3390/polym18212800

Authors: Petr Slepička Iva Labíková Bára Frýdlová Matěj Budina Petr Sajdl Václav Švorčík Nikola Slepičková Kasálková

In this study, we present the development of biopolymer honeycomb (HCP PLLA) microstructures on plasma-modified PTFE polymer using the improved phase separation method with the aim of preparing a surface with enhanced cytocompatibility. To determine changes in surface morphology and characterize the size and shape of the prepared PLLA microstructures, laser confocal microscopy (LCM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) methods were used. To determine the chemical composition of the surface of substrates modified with the formed HCP PLLA microstructures, X-ray photoelectron spectroscopy (XPS) was used. PTFE samples modified with an 8 W plasma discharge proved to be a suitable material for further study as a substrate for honeycomb patterns and biocompatibility testing. It was found that the formation (size) of PLLA microstructures is influenced not only by the exposure time of the samples in plasma but also by the PLLA content in the coating solution and the thermal stress of the material. Plasma modification and subsequent phase separation significantly increased the surface amount of oxygen and carbon and suppress the surface amount of fluorine to a minimum, which is evidence of almost 100% coverage of the PTFE surface with the PLLA coating solution. Biocompatibility testing on selected PTFE samples revealed that modification with 8 W plasma in combination with HCP microstructures—created by the phase separation method in solution with 3 wt. % PLLA—leads to significant support for SaOS-2 osteoblast cell proliferation. This study highlights the potential of biopolymer honeycomb pattern surfaces with engineered topography for advanced biomedical applications.

Polymers doi: 10.3390/polym18212799

Authors: Ali Reza Torabi Media Naeimayi Andres Garcia Granada Majid Reza Ayatollahi

Material extrusion (MEX) is an extensively used additive manufacturing technique that facilitates the fabrication of precise physical components with complex geometries through successive material deposition. However, the anisotropic behavior inherent to MEX-printed materials can substantially influence their fracture response. This study examines the fracture behavior of U- and blunt V-notched (BV-notched) MEX-printed Acrylonitrile Butadiene Styrene (ABS) under symmetrical three-point bending using rectangular specimens with a symmetrical [0/90]s cross-ply printing architecture. To this end, three different notch root radii within the 1–4 mm range are experimentally investigated, and the measured fracture loads are compared with theoretical-numerical predictions obtained by integrating the virtual isotropic material concept (VIMC) with four failure models, namely the point stress (PS), mean stress (MS), and averaged strain energy density (ASED) criteria, as well as the extended finite element method coupled with a cohesive zone model (XFEM-CZM). All four VIMC-based criteria provide reasonable correspondence with the experimental results. Among them, the ASED-VIMC criterion exhibits the lowest average percentage difference of 5.7% for the 1–4 mm range of notch root radius, symmetrical [0/90]s cross-ply printing architecture, and symmetrical three-point bending, followed by the PS-VIMC criterion with 7.4%. ASED-VIMC criterion also demonstrates the most consistent performance for both notch configurations, likely due to its lower sensitivity to notch geometry.

Polymers doi: 10.3390/polym18212798

Authors: Qi Lu Xian Zhou Xian Wu Zeyu Fan Peihang Li Wei Han

High-strength polyethylene-fibre engineered cementitious composites (PE-ECCs) provide tensile strain hardening and distributed cracking, but their high paste content and low water-to-binder ratio produce substantial shrinkage. This study conducted a multi-criteria screening of an MgO expansive agent and a shrinkage-reducing admixture (SRA) in a PE-ECC repair mortar for hydraulic-concrete applications. The reference matrix contained 65% P·II 52.5 cement, 10% silica fume, 25% blast-furnace slag, a water-to-binder ratio of 0.27, and 2.5 vol.% PE fibre. Drying shrinkage, compressive and flexural strengths, tensile response, crack number, and strain-based crack-opening estimate were assessed. The reference mortar reached 90.1 MPa compressive strength and 6.6% tensile strain but developed 1489 με of 28 d shrinkage. 2% MgO reduced the 28 d shrinkage to 1384 με, whereas higher dosages shifted from contraction to net expansion and reduced tensile performance. The liquid SRA reduced 28 d shrinkage to 982, 930, and 874 με at 1%, 2%, and 3%, respectively. The 1% mixture retained 82.3 MPa compressive strength, 5.7 MPa tensile strength, 4.4% tensile strain, and a crack-opening estimate of 66.4 μm. Under the adopted criteria, 1% SRA provided the most balanced combination of dimensional stability, strength, and tensile ductility, making it a candidate for application-specific evaluation in hydraulic-concrete repair.

Polymers doi: 10.3390/polym18212797

Authors: Oluwaseyi Matthew Abioye Oluwaseun Temitope Faloye Timothy Adesoye Adekanye Matthew Folorunsho Amodu Abiodun Afolabi Okunola Oluwafemi E. Adeyeri Laemthong Laokhongthavorn Viroon Kamchoom

Petroleum-based plastics generate over 400 million tonnes of waste annually, posing severe ecological threats to terrestrial and aquatic environments. Concurrently, water hyacinth (Eichhornia crassipes, Mart.) infests over 50 countries, disrupting waterways, fisheries, and riparian economies. This review proposes that both challenges can be addressed within a single material strategy: valorizing water hyacinth biomass into cellulose-derived bioplastics, nanocellulose composites, and functional hydrogels. To organize the evidence, the review uses a conceptual Harvest–Extract–Formulate–Deploy (HEFD) scheme that follows the value chain from field harvest through cellulose extraction, composite formulation and crosslinking to end use. The scheme is a structuring device and not a validated model. The review draws on the peer-reviewed literature published between 2018 and 2026 and examines composition, mechanical and thermal performance, synthesis routes, and applications in packaging, agriculture and biomedicine. Water hyacinth is not a plastic in itself but a variable lignocellulosic raw material, and the properties of materials made from it depend mainly on the matrix polymer, filler content, and the interface between the two. Reported tensile strengths are modest and elongation at break is far below that of low-density polyethylene (LDPE), so equivalence with LDPE has not been shown. Mass loss in soil-burial tests ranges from a few percent to near-complete disintegration depending on the formulation, and few studies measure mineralization. Feedstock may be cheap, or even paid for, where removal is publicly funded, but no peer-reviewed techno-economic study has confirmed this advantage. A decentralized small-scale production model is proposed for tropical smallholder settings, and clear gaps remain in life-cycle assessment, standardization, and regulation.

Polymers doi: 10.3390/polym18212796

Authors: Wail Falath

Chlorine resistance of reverse osmosis membranes is usually reported as the fraction of salt rejection retained after chlorination, a metric that depends on the initial rejection. This secondary reanalysis quantifies the dependence for published data on substrate-free poly(vinyl alcohol) (PVA) membranes containing multi-walled carbon nanotubes (MWCNT), Gum Arabic (GA) or graphene oxide (GO). Within the solution–diffusion model, the change in salt passage was expressed as an observed ratio, kR, which also includes any change in flux or swelling and is not a direct measure of chemical degradation. Judged by rejection retention, all three fillers reduced the relative rejection loss about tenfold at their best-performing loadings. Relative to each study’s control, however, GO produced no consistent reduction in kR across loadings (3.11 ± 0.48 versus 3.20); MWCNT produced a moderate reduction (1.16–1.49 versus 1.76) and GA a reduction only at 0.1–0.5 wt%; these differences persisted, marginally for MWCNT, at rejection uncertainties of two percentage points. For GO and GA, most or all of the apparent improvement (97–111% in the more robust decomposition order) reflected the higher initial rejection. Rejection retention therefore overstates the benefit of fillers that raise selectivity; the salt-passage ratio offers a simple correction when post-exposure flux is unavailable.

Polymers doi: 10.3390/polym18212795

Authors: Thomas Rodríguez-Peña Edwin Collado Yessica Saez Nacari Marin-Calvo

Titanium dioxide (TiO2) is incorporated into polylactic acid (PLA) to improve stiffness, promote crystallization, and provide ultraviolet (UV) shielding. However, its influence on durability is complex, as photocatalytic activity may accelerate degradation under environmental exposure. This review examines how TiO2 characteristics, melt processing history, fused filament fabrication (FFF) architecture, and exposure conditions collectively influence PLA durability. Primary studies and previous reviews are critically compared based on material formulation, processing conditions, specimen geometry, environmental exposure, and measured properties. Evidence indicates that reprocessing generally reduces molar mass and melt viscosity, while crystallization and printing conditions may partially preserve mechanical performance. TiO2 can enhance selected properties, although its effects depend on particle characteristics, dispersion, and surface accessibility. Furthermore, interlayer interfaces and connected porosity influence moisture transport and damage localization, limiting the applicability of findings from films and moulded specimens to FFF components. While existing reviews have addressed PLA–TiO2 composites and their properties, the combined influence of reprocessing, TiO2 incorporation, FFF architecture, and tropical weathering has received limited attention. Unlike previous reviews that primarily examine these factors separately, this review integrates their potential interactions to provide a processing-history-dependent perspective on PLA durability. It also identifies research priorities involving controlled processing comparisons, multiscale characterization, and complementary natural and accelerated weathering tests to support more reliable assessments of outdoor performance.

Polymers doi: 10.3390/polym18212794

Authors: Yassine El-Ghoul Sami M. Alharbi Suliman S. Aba-alkhayl Bechir Hammami

The development of multifunctional wound dressings based on bioactive polymers offers an opportunity to combine moisture management, structural stability, and biological functionality within a single material. However, the integration of crosslinked agar/κ-carrageenan coatings, a poly(acrylic acid)/sodium hypophosphite (PAA/SHP) crosslinking system, and propolis on cellulosic textile substrates, together with the relationships between material properties and in vitro biological responses, warrants further investigation. In this study, a functionalized cellulosic textile incorporating agar, κ-carrageenan, PAA, SHP, and propolis (PS) was prepared and characterized. The curing conditions of 140 °C for 15 min were selected based on previous work and adopted in the present study. The resulting materials were characterized by ATR-FTIR spectroscopy, scanning electron microscopy (SEM), swelling measurements, and tensile testing. The functionalized textiles exhibited a mass gain of 23.03% and a swelling ratio of 630%, indicating substantial material incorporation and water uptake. The wet breaking force reached 4.89 N, demonstrating measurable mechanical performance under hydrated conditions. ATR-FTIR findings were consistent with chemical interactions associated with the proposed PAA-mediated crosslinking mechanism, while SEM revealed morphological features consistent with the formation of a polymeric coating on the cellulose fibers. The complete formulation exhibited an apparent relative HepG2 MTT response of 132.5% after 72 h, indicating metabolic activity above that of the control under the tested conditions. The propolis-containing materials also exhibited antibacterial activity against the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli, with inhibition zones of 39.2 mm and 29.3 mm, respectively, and demonstrated antifungal activity against Candida albicans. Further evaluation using MCF-7 breast cancer cells and non-tumorigenic MCF10A breast epithelial cells revealed differential cellular viability responses. MCF-7 cell viability decreased to 25.4% and 17.2% after 24 and 48 h, respectively, under the tested conditions. These findings highlight the material’s water-absorption capacity, mechanical performance, antimicrobial activity, and differential cell-based responses. The novelty of this study lies in integrating these components within a cellulosic textile and evaluating its physicochemical, mechanical, antimicrobial, and cellular responses. Overall, the results support further investigation of the prepared material as a candidate bioactive wound dressing. Nevertheless, additional studies are required to establish the nature and extent of covalent grafting, quantify propolis loading and release, and assess compatibility with wound-relevant cells, particularly human dermal fibroblasts and keratinocytes.

Polymers doi: 10.3390/polym18212793

Authors: Baki Bağrıaçık İlkim Özbahçeci Gökdeniz

In developing and currently developed countries, dealing with solid wastes comprises one of the ultimate social, economical and environmental problems. Thus, geotechnical engineers have recently been in search of alternative waste materials in regard to the utilization of wastes in soil stabilization procedures. Construction demolition wastes, which constitute a significant part in the mentioned solid waste materials, have come to mind as an alternative to be implemented in such applications. By means of considering the utilization of these wastes, one aim has been to reduce both the amount of accumulated waste to the environment and related costs of stabilizing problematic soil conditions. Within the context of this study, improvability of fine-grained soils was questioned by means of utilizing alkaline activators to geopolymerize construction demolition wastes in order to procure an alternative material to cement. Eventually, optimum values for the considered NaOH, KOH and CaO alkaline activators were determined to be 8, 8 and 6 molal, respectively. The use of KOH, NaOH, and CaO activators during the geopolymerization process resulted in a significant improvement in bearing capacity compared with the untreated waste–soil mixtures. This finding indicates that these activators can be effective in enhancing the engineering performance of waste–soil mixtures. Among the activators investigated, NaOH exhibited the highest effectiveness in improving bearing capacity, yielding superior results compared with KOH and CaO. The superior performance of NaOH is considered to be potentially associated with its ability to promote the formation of a binding structure and facilitate interactions among the mixture constituents more effectively during geopolymerization. The resulting binding structure may strengthen the interparticle bonds between the soil and waste particles, thereby contributing to an improvement in the load-bearing capacity of the mixture. Therefore, based on the findings obtained, NaOH was concluded to be the most effective activator for enhancing bearing capacity under the conditions investigated. Additionally, temperature increments resulted in enhancements in the bearing capacities, and the maximum value was reached at the completion of day 28. Moreover, time-dependent settlements reduced by approximately up to 5.76–5.78 times. Consequently, it was observed that the geopolymerization method can be considered as a decent enough and novel alternative to cement for the improvement of engineering properties of fine-grained soils at significant ratios.

Polymers doi: 10.3390/polym18212792

Authors: Erkan Yılmaz

Sandwich structures with gyroid cores produced via additive manufacturing show promise for lightweight impact-absorbing applications due to the stable plateau response provided by their continuous surface geometries; however, the effect of post-printing thermal history on the impact behavior of these structures has not been sufficiently investigated. In this study, three sandwich configurations were produced with 2 mm face sheets, a 10 mm core thickness, and a 10 mm gyroid cell size: all-PA6, all-PA6-CF, and a hybrid structure consisting of PA6-CF face sheets and a PA6 core. Non-heat-treated (Non-HT) and heat-treated (HT, 170 °C for 4 h) specimens were subjected to low-velocity impact at energy levels of 5, 10, 15, 20, and 25 J; peak force, absorbed energy, energy absorption efficiency (the ratio of absorbed energy to impact energy), and specific energy absorption (SEA) were compared. The effect of heat treatment depended on the material configuration and impact energy. DSC analyses showed that heat treatment increased the degree of crystallinity in PA6-CF from 6.4% to 11.4%, while in PA6, it increased only from 6.2% to 6.7%. In the PA6-CF configuration, heat treatment reduced the peak force by 28% and 34% at 15 and 20 J, respectively (8.41→6.04 kN; 8.20→5.42 kN), while increasing the absorbed energy from 17.5 J to 19.8 J at 20 J and giving the highest SEA of 0.243 J/g at 25 J. In the unreinforced PA6 configuration, heat treatment reduced the absorbed energy at 25 J from 15.7 J to 11.3 J and the energy absorption efficiency from 63% to 45%. The hybrid configuration exhibited the most stable response, with efficiencies of 92–101% in both cases within the 10–20 J range and limited peak forces in the 2.6–3.4 kN range. The findings indicate that post-printing heat treatment is an effective parameter for adjusting impact performance without changing the geometry or material, but that the direction of its effect depends on the presence of fiber reinforcement and the impact energy.

Polymers doi: 10.3390/polym18212790

Authors: Dariusz Kowalczyk Karolina Wójciak Paulina Kęska Monika Basiura-Cembala Tomasz Skrzypek

This study evaluated gelatin (GEL)-based edible coatings as a complementary preservation approach for sliced cooked cured pork loin (CCPL) vacuum-packaged in polyamide/polyethylene (PA/PE) film and stored at 4 °C for 21 days, focusing on the effect of GEL concentration (5% vs. 10%) on film properties and coating performance. GEL films were characterized at 40–90% relative humidity (RH), with PA/PE film as a benchmark. Despite the more compact cryo-SEM microstructure of the 10%-GEL film/coating-forming solution network, the resulting films showed no significant differences in microstructure, crystallinity, or most physicochemical properties. Compared with the PA/PE, GEL films exhibited a more compact structure, higher transparency, stronger UVB/UVC-blocking capacity, lower oxygen permeability at 40–60% RH (127.75–1231.25 vs. 4234.06–5056.72 cm3 μm m−2 d−1), and higher puncture strength at RH ≤ 70% (9.12–15.24 vs. ~6.6 MPa). Increasing RH elevated oxygen permeability in all films and moisture uptake in GEL films, thereby reducing their mechanical strength. Coating application was associated with reduced oxidative stability and increased microbial counts, with effects varying by GEL concentration and storage time. These findings demonstrate that favorable film properties measured under standard conditions do not necessarily translate into effective preservation of meat products when employed as edible coatings.

Polymers doi: 10.3390/polym18212791

Authors: Samanwita Bhattacharya Nirjhar Bar Baisali Rajbansi Sudip Kumar Das

The study aims to use Chitosan/nSiO2 Nanocomposite (CSNC) as an adsorbent to eliminate toxic Cu(II) ions from its aqueous solution using a fixed-bed continuous column system. nSiO2 was synthesized from rice husk ash. The adsorption investigations were performed at optimum pH 6.5 under different operating conditions, such as bed height (3–7 cm), influent flow rates (30–50 mL min−1), and influent Cu(II) concentration (10–30 mg L−1). The removal of Cu(II) was increased with the column’s bed depth but reduced with flow rate and adsorbate concentration. Experimental observations were employed to study seven kinetic models. The Thomas model was confirmed to be the best-fit kinetic model corresponding to 3 cm bed height, a column diameter of 1.5 cm, 30 mL min−1 flow rate, and an initial metal concentration of 30 mg L−1. A regeneration study and scale-up design were also reported. MLR (R2 > 0.98) and GA techniques (R2 = 1) were also applied to forecast the elimination of Cu(II). The performance of the prepared nanocomposite adsorbent was evaluated on a laboratory scale for removing Cu(II) from synthetic wastewater. This study integrates sustainability and circular economy principles in the application of adsorbents by focusing on their synthesis, utilization in fixed-bed continuous column systems, regeneration, and safe disposal.

Polymers doi: 10.3390/polym18212789

Authors: Hebrón Vázquez-Estudillo Giovanni Palomino-Vizcaino Brisa G. Hernández-Ramírez Lilia A. Hurtado-Ayala Jonathan Vincent Lopez-Baena Teresa G. Rodriguez-Tellez Iván Cordova-Guerrero Lucia E. Azuara-Alvarez Arturo Estolano-Cobián Kenia Palomino-Vizcaino José M. Cornejo-Bravo Héctor Magaña

Polymeric prodrugs capable of pH-responsive drug release are promising platforms for localized and controlled drug delivery. While positional isomerism is known to affect the physicochemical properties of MBA polymers, a comparative evaluation of its effect on drug release kinetics and biological activity is lacking. In this study, three methacryloyloxybenzoic acid (MBA) polymeric prodrugs derived from ortho-, meta-, and para-hydroxybenzoic acid (HBA) isomers were synthesized to comparatively evaluate the influence of substituent position on HBA release profiles and biological performance. The o-, m-, and p-MBA monomers and their corresponding polymers were synthesized and structurally characterized by FTIR-ATR, 1H-NMR and UV-Vis spectroscopy. HBA release profiles investigated under physiologically relevant pH conditions revealed markedly distinct release profiles among the polymers. Poly(o-MBA) exhibited rapid and near-complete release at intestinal and physiological pH, poly(p-MBA) showed sustained and intermediate release, and poly(m-MBA) displayed minimal release under all tested conditions, indicating that substituent position strongly influences HBA release, likely through differences in ester accessibility and hydrolytic susceptibility. The polymers also exhibited planktonic antibacterial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, while BALB/3T3 fibroblast viability remained above 70% at a concentration of 0.5 mg/mL. These findings indicate that positional isomerism is a key structural determinant of pH-responsive release kinetics in MBA polymers and highlight their potential as versatile platforms for pharmaceutical and biomedical applications, particularly in the design of localized and controlled drug delivery systems.

Polymers doi: 10.3390/polym18212788

Authors: Selma Jakupović Damir Duratbegović Nedim Pervan Enis Muratović Vedran Jakupović

Alkasites are resin-based restorative materials that differ from conventional resin composites in the composition and reactivity of their filler system, which enables ion release. Whether optional light activation changes the mechanical properties of the alkasite Cention Forte, compared with self-curing and with a conventional composite, remains insufficiently documented. This in vitro study compared Cention Forte (urethane dimethacrylate-based matrix; reactive calcium fluorosilicate and barium glass fillers) in self-cured (G1) and light-cured (G2) modes with the nanohybrid composite Tetric EvoCeram (G0; dimethacrylate matrix; barium glass, ytterbium trifluoride, mixed oxide and prepolymerized fillers). Top- and bottom-surface Vickers microhardness (VMHt, VMHb), bottom-to-top ratio (BTR), diametral tensile strength (DTS) and compressive strength (CS) were measured (n = 7). G1 showed the highest VMHt (70.3 HV), followed by G0 (63.0 HV) and G2 (57.8 HV) (p< 0.001). Both Cention Forte groups had BTR values of approximately 1.00 (G0: 0.97) as an indirect, surface-based index. G2 exhibited the highest DTS (39.7 MPa) and G0 the highest CS (311.2 MPa). Curing mode accounted for most between-group variance in microhardness, whereas material composition dominated compressive strength.

Polymers doi: 10.3390/polym18212787

Authors: José Javier Coca-Hidalgo Carlos Peniche-Covas Jaime Lizardi-Mendoza Waldo Manuel Argüelles-Monal

Chitosan grafted with N-alkyl-substituted polyacrylamide yields dual-responsive materials sensitive to both pH and temperature. For instance, the phase transition of poly(N,N-diethylacrylamide) can be tuned by copolymerizing it with more hydrophilic units, such as N,N-dimethylacrylamide or N-ethylacrylamide. While hydrophilic and hydrophobic interactions between macromolecular segments drive this phase transition, the specific role of hydrogen bonding between chitosan and the polyacrylamide grafts is not fully understood yet. Clarifying how these interactions influence the volume phase transition is essential for predicting hydrogel behavior. Chitosan-g-poly(DEAm-co-DMAm) and chitosan-g-poly(DEAm-co-NEAm) hydrogels showed continuous volume phase transitions that broadened with increased content of hydrophilic units (DMAm or NEAm). The critical temperature (Tc) of chitosan-g-poly(DEAm-co-DMAm) hydrogels increased linearly with the content of DMAm, while chitosan-g-poly(DEAm-co-NEAm) hydrogels exhibited a downward deviation from the linear variation in Tc from 0 to 100 mol-% DEAm. Both hydrogels showed higher swelling in acidic conditions at temperatures below the Tc, with a marked reduction as pH turned basic. Above the Tc, the pH response was almost negligible. Evidence suggests that the formation of hydrophobic domains of N,N-diethylacrylamide units during heating could bring the N-alkyl polyacrylamide and the chitosan chains closer together. This promotes inter-chain hydrogen bonding, which favors the cooperative character of the transition.

Polymers doi: 10.3390/polym18212786

Authors: Laura Cortés Corrales Sonia Domínguez Tejedor Harshit Sahai Mengyan Huang María Jesús Martínez Bueno María Dolores Hernando Amadeo R. Fernández-Alba

Respiratory exposure to microplastics (MPs) remains poorly quantified because most tissue-based studies neither report extraction recovery efficiency nor assess whole-organ burden. Using lamb lungs as a model, we validated a method for determining MP burden in lung tissue by comparing three digestion oxidants and three sample masses against four spiked reference polymers:polypropylene(PP),polystyrene (PS),low-density polyethylene (LDPE) and polyethylene terephthalate (PET). Sodium persulfate (Na2S2O8) digestion of 10 g freeze-dried tissue (~25% of the lamb lung) gave the best recovery (~70%) and was applied to lung tissue from captive-held Saharan ungulates (two adult gazelles, a pregnant gazelle with two fetuses, and a neonatal aoudad). Across the adult gazelles, fibres dominated the internal burden, with PP enriched among fragments and PET dominant among fibres, confirmed by micro-Fourier- transform infrared spectroscopy (µFTIR). Particles were overwhelmingly coarse (mostly 30 to ≥100 µm), with essentially none meeting respirable (<10 µm) or alveolar-like (<4 µm) size criteria, consistent with retention in conducting airways rather than alveolar deposition. No MPs were detected in either fetus or in the neonatal aoudad, suggesting postnatal rather than prenatal accumulation of pulmonary burden. This is, to our knowledge, the first recovery-characterized, whole-lung (one animal) and per-gram tissue-level (two animals) burdens in captive-held ungulates, providing a transferable framework for assessing respiratory MP exposure in captive-held life and livestock.

Polymers doi: 10.3390/polym18212785

Authors: Hassan Shuaibu Abdulrahman Michael Chiahemba Iorpenda Muhammed Fatih Yentimur Ali Almusawi Mustafa Albdairi

Recycled high-density polyethylene (HDPE) and waste engine oil (WEO) can be combined to modify bitumen, but the high-temperature performance of such binders is often judged from oscillatory measurements alone. This study compares the oscillatory and creep–recovery responses of two long-term-aged HDPE/WEO binders with the same total modifier content but different HDPE:WEO ratios with those of the unmodified base bitumen. Dynamic shear rheometer (DSR) temperature sweeps and multiple stress creep recovery (MSCR) tests, also performed on the DSR, were combined with fractional viscoelastic modeling. Both blends reduced the non-recoverable creep compliance by a factor of 3.8–7.3, so the modification improved the resistance to permanent deformation. In oscillation, however, the blends became more elastic as the temperature increased, whereas in creep, they recovered almost no strain and crept 2–122 times more than predicted from their oscillatory response; the base bitumen was predicted within a factor of 1.6. The creep response of the blends was also four to five times more temperature-sensitive than their oscillatory response. A three-parameter fractional Maxwell model described all creep–recovery cycles and captured the power-law recovery of the blends better than the Burgers model. The results are consistent with an HDPE-rich structure that dominates the oscillatory response but breaks down at MSCR strains, so oscillatory stiffness overstates both the elastic character and the magnitude of the improvement achieved by the binders tested.

Polymers doi: 10.3390/polym18212784

Authors: Eugenia Battellocchi García María José Gómez Ramos María Dolores Hernando Guil Laura Cortés Corrales Chen Wang José Luis Oller Serrano Harshit Sahai Maria Jesús Martínez Bueno Amadeo Rodríguez Fernández-Alba

Airborne microplastics (MPs) are emerging contaminants of concern in school environments, where children may experience prolonged exposure. This study assessed airborne MPs at three Spanish schools located in contrasting settings: a dense urban area in Madrid (A), a residential area in Almería (B), and an agricultural peri-urban area in Almería surrounded by greenhouses (C). An additional simultaneous indoor–outdoor comparison was performed at School B. Air samples were collected using active samplers with 25 µm stainless-steel meshes, and particles were characterised by stereomicroscopy, µ-FTIR spectroscopy, FESEM, and FTIR. Fibres were the predominant morphology, and polyethylene terephthalate (PET) was the most abundant synthetic polymer. School A showed the highest abundance of synthetic fibres, while polymer composition differed significantly among schools (χ2 (12) =41.77, p < 0.0001). Indoor samples contained more particles than outdoor samples, although natural-to-synthetic proportions were similar; PP, PA, and PE contributed relatively more indoors, whereas PET predominated outdoors. Only 0.45% and 0.13% of particles fell within the <10 µm and <4 µm estimated aerodynamic-size ranges, respectively, all being fibres. Overall, airborne MP occurrence varied with location and indoor–outdoor setting, while selected PET and PP fibres showed polymer-dependent surface and chemical alteration.

Polymers doi: 10.3390/polym18212782

Authors: Carmen Elena Pérez-Cervera Daniela Colorado-Triana Camila Andrea Suarez-Gómez María Alejandra Castillo-Ortega Mateo Ávila-Díaz Claudia Denise De Paula Ricardo David Andrade-Pizarro

Steam precooking of starch-rich raw materials yields pregelatinized biopolymer matrices; however, how the structural state of starch in multicomponent precooked flours relates to their hydration, pasting, flow, and dough and batter viscoelastic behavior remains poorly documented. This study developed and characterized a steam-precooked composite flour (PCF) from cowpea (Vigna unguiculata), unripe plantain (Musa paradisiaca cv. Hartón), and orange-fleshed sweet potato (Ipomoea batatas cv. Agrosavia Aurora), formulated using linear programming to meet the nutritional targets set by the “Instituto Colombiano de Bienestar Familiar” (ICBF). The PCF contained 24.08 ± 0.13% crude protein, 375.1 kcal/100 g, and 89.23 ± 0.18% in vitro protein digestibility, exceeding the ICBF minimum requirements. Differential scanning calorimetry showed no defined gelatinization endotherm, only a weak, broad endothermic region (52–92 °C; ΔH = 2.35 ± 0.56 J/g dry flour) attributed mainly to retrograded amylopectin and a minor residual starch fraction; the pasting profile lacked a viscosity peak, with breakdown indistinguishable from zero. Flour suspensions exhibited pseudoplastic behavior (shear-thinning), with a flow behavior index of 0.542 and a consistency coefficient of 0.311 Pa·sⁿ, and a flat pasting profile with negligible breakdown (0.02 cP), consistent with a collapsed structure. Cookie dough and muffin batter behaved as weak elastic gels (G′ > G″), with cookie dough approximately two orders of magnitude stiffer than muffin batter, though both showed a similar critical strain (8–13%) at the solid-to-flow transition. Baked cookies and muffins achieved high sensory acceptance and purchase intention (84% for cookies, 80% for muffins). These results suggest that PCF is a promising local alternative, with adequate nutritional, technological, and sensorial performance, to fortified blended foods based on imported ingredients for bakery products.

Polymers doi: 10.3390/polym18212783

Authors: Mücahit Çalışan İbrahim Ayaz

Predicting the glass transition temperature (Tg) of polymers from structures remains difficult, and whether descriptors and molecular-language embeddings carry complementary information is unclear. CDEF-Tg (Compact Descriptor–Embedding Fusion for Glass Transition Temperature Prediction) concatenates 205 RDKit descriptors (RDKit205) with a frozen 384-dimensional ChemBERTa embedding (ChemBERTa384) and maps the 589-dimensional vector to Tg with an ExtraTreesRegressor. It was evaluated on 10,065 identity-resolved records of a polyimide-oriented dataset under three leakage-safe protocols: IID Group-Safe (IID, independent and identically distributed), Scaffold OOD (OOD, out-of-distribution), and Similarity OOD (T = 0.90). The model was selected on validation evidence and frozen before the final-test sets were opened. In the locked final test, CDEF-Tg reached a macro mean absolute error (MAE) of 48.84 °C, versus 50.17 °C (RDKit205 alone) and 54.33 °C (ChemBERTa384 alone). Group-aware bootstrap analyses separated CDEF-Tg from RDKit205 alone in MAE only under Similarity OOD and showed no MAE advantage over the comparator RDEF-Tg. Additional validation-only controls showed a lower macro MAE for a Morgan-fingerprint partner than for CDEF-Tg (49.11 versus 53.15 °C), and ChemBERTa384 lowered LightGBM error; the ExtraTrees ordering was stable across random states (split seeds were not varied). The results suggest a modest, protocol-dependent benefit within this dataset; the additional analyses provide descriptive evidence.

Polymers doi: 10.3390/polym18212781

Authors: Cristina Pavon Cristina Mellinas María Carmen Garrigós Alfonso Jimenez Juan López-Martínez

Gum rosin (GR) is a natural and renewable polymer resin obtained from pine trees with potential in medication delivery applications. This work uses electrospraying to obtain and characterize GR microspheres (eGR) containing zinc phthalocyanine (ZnPc), a synthetic blue-green macrocyclic chemical with photosensitive properties. Electrospraying effectively created uniform microspheres with high encapsulation efficiency. A ZnPc release profile was performed, and it was observed that it quickly evolved during the first 24 h, reaching 0.438 mg per 100 g of sample and peaking at 0.868 mg per 100 g after 72 h. The subsequent decline is presumably due to the high hydrophobicity of free ZnPc, leading to its precipitation or adsorption onto the container. Nuclear magnetic resonance (NMR) analysis demonstrated the interaction between ZnPc and GR, confirming the successful formation of microspheres. Zeta potential analysis indicated that both eGR and eGR-ZnPc microspheres had negatively charged surfaces, likely due to anion adsorption or the presence of functional groups. The initial zeta potential values were −80.6 ± 3.3 mV for eGR and −74.1 ± 5.6 mV for eGR-ZnPc, reflecting the high stability of microspheres. However, stability decreased after 120 h due to particle aggregation, with a 70% drop in zeta potential after 360 h. No significant differences were observed between formulations during stability tests.

Polymers doi: 10.3390/polym18212780

Authors: Laura Vignau Arsuaga Aloña Retegi Irati Berasarte Loli Martin Arantxa Eceiza Nagore Gabilondo

Active poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofiber membranes incorporating antioxidant extracted coffee oil (ECO) from spent coffee grounds were prepared by electrospinning. GC-MS analysis revealed similar proportions of saturated and unsaturated fatty acids, predominantly linoleic (37%) and palmitic (35%) acids, followed by oleic/elaidic (9%) and stearic (8%) acids. ECO exhibited antioxidant activity in DPPH and ABTS assays (82 and 51 μmol Trolox equivalents, respectively), with a total phenolic content of 22 mg gallic acid equivalents per gram. Single-needle electrospinning produced membranes containing 8–30 wt% ECO, while coaxial electrospinning of an ECO core and PHBV shell yielded membranes containing 15 wt% ECO. Thermal, morphological, surface, mechanical, and antioxidant properties were investigated. Single-needle electrospinning produced continuous, bead-free nanofibers, whereas TEM observations suggested a core–shell structure in coaxial fibers. ECO incorporation increased fiber diameter (465–586 nm for single-needle and 542–619 nm for coaxial fibers), promoted fiber junctions and surface wettability, and significantly improved mechanical strength, particularly at the highest ECO loading. All ECO-loaded membranes showed radical scavenging activity, with coaxially electrospun membranes exhibiting DPPH inhibition (44%) comparable to that of single-needle membranes containing twice the ECO loading. These findings support the potential of ECO-loaded PHBV nanofibers as active membranes.

Polymers doi: 10.3390/polym18212779

Authors: Md Murshed Bhuyan Kyungjun Lee

Gel polymer electrolytes are attractive quasi-solid electrolyte systems that combine the high ionic mobility and electrode wetting of liquid electrolytes with the dimensional stability and reduced leakage of polymer networks. Their value for high-performance lithium-ion batteries is increasingly determined not only by bulk ionic conductivity, but also by Li+ selectivity, solvent retention, mechanical integrity, electrochemical stability, and the ability to form stable interfaces with high-voltage cathodes and practical graphite and Si-containing anodes. This review critically summarizes recent progress in GPEs through a structure, transport, interface-performance framework, with particular emphasis on developments reported in recent years while retaining foundational studies that established the field. Representative polymer hosts, including PVDF/PVDF-HFP, PEO, PAN, PMMA and methacrylate networks, cellulose-derived matrices, and emerging functional polymers, are compared according to their molecular functionality and practical limitations. Major performance-enhancement strategies-including blending, crosslinking, inorganic or nanostructured fillers, functional additives, nonflammable components, self-healing chemistries, and in situ polymerization-are then evaluated in terms of how they regulate ion transport, interphase chemistry, mechanical behavior, thermal safety, and manufacturability. Recent demonstrations in NCM/graphite and NCM/Si graphite pouch cells show that conformal in situ gelation, LiF-rich interphases, adaptive network mechanics, and low-reactivity liquid phases can translate materials-level improvements into high-rate cycling, long life, and improved abuse tolerance. Remaining challenges include conductivity, mechanical strength, high-voltage oxidation and wide-temperature operation. Future GPE development will therefore require integrated molecular, interfacial, and cell-level design rather than optimization of isolated membrane properties.

Polymers doi: 10.3390/polym18212778

Authors: Entesar A. Ganash Salihah A. Al-zahrani Hala A. Al-Jawhari Reem M. Altuwirqi

The increasing global water scarcity, driven by population growth, industrialization, and climate change, has created an urgent need for sustainable and efficient water desalination. This study focuses on developing a solar-driven steam generation (SSG) desalination system that uses photothermal materials (PTMs), such as molybdenum disulfide (MoS2) and graphene produced via laser-induced graphene (LIG), to enhance evaporation efficiency. The system was prepared by coating melamine foam (MF), used as the base, with polyvinyl alcohol (PVA) at varying concentrations (0.6 wt%–1.4 wt%), with the 1 wt% concentration showing the highest evaporation rate. MoS2 (1 wt%) was incorporated to improve light absorption. The final step involved graphitization and surface modification via the LIG technique, using a 450 ± 5 nm visible laser to induce structural changes. The effects of laser power and scribing density (Lines-Per-Inch, LPI) on the evaporation rate and efficiency were investigated. The optimal configuration, consisting of 1 wt% PVA, 1 wt% MoS2, 0.5 W laser power, and 300 LPI, significantly enhanced light absorption to 77%, compared with 65% in the baseline sample. This Janus configuration achieved an evaporation rate of 1.925 kg m−2 h−2 in saline water (3.5% sodium chloride (NaCl)) under 1 kW/m2 solar irradiance, corresponding to an apparent evaporation efficiency of ~98%. The integration of material engineering improves the SSG system’s performance. The system demonstrated excellent stability over 10 cycles in a saline environment, with no significant performance degradation. Using the combined advantages of PVA, MoS2 and LIG offers a scalable, cost-effective, and energy-efficient approach, making it a promising system for sustainable desalination and the water scarcity crisis.

Polymers doi: 10.3390/polym18212777

Authors: Kaixin Guo Peixing Yang Zhaohui Min Jinxiang Hong

High-modulus asphalt mixtures (HMAMs) achieve high stiffness but exhibit insufficient resistance to low-temperature cracking. To balance high- and low-temperature performance, HMAMs containing 0.3%, 0.6%, and 1.0% high-modulus modifier (HMM) were toughened with a styrene–butadiene-based polymer (SBP) through a dry process. The toughening behavior and mechanisms were investigated at different SBP dosages (0.2%, 0.4%, and 0.6%) and conditioning times using mixture tests, binder rheological characterization, individual and co-swelling tests, and molecular dynamics simulations. Increasing HMM content substantially improved dynamic modulus and rutting resistance but continuously reduced low-temperature bending strain. At 0.4%, SBP provided favorable strength–deformation compatibility, increasing bending strain by 76.1%, 75.3%, and 63.2% in the three HMM systems, respectively. The optimal conditioning time extended from 30 min (0.3% HMM) to 60 min (0.6% and 1.0% HMM). The 0.6% HMM–0.4% SBP combination exhibited the most balanced overall performance. Rheological results showed that HMM enhanced high-temperature elasticity, whereas SBP reduced low-temperature creep stiffness and improved stress relaxation. With limited availability of light fractions, increasing HMM from 0.3% to 1.0% reduced the swelling ratio of SBP from 114.87% to 62.30%. Molecular simulations further showed that HMM–light fraction interactions increased, whereas the magnitude of the SBP–light fraction interaction energy decreased by 13.2%. These findings suggest that competition for limited light fractions may contribute to the HMM-dependent toughening response, providing a basis for further investigation of material composition and conditioning requirements.

Polymers doi: 10.3390/polym18212776

Authors: Qihang Zhou Haobing Fu Ningyang Feng Tusheng He Huaqiang Cheng Jie Chen Jinhui Li Zi Yu Wei Du Leheng Li Qingjun Ding

High-strength concrete applied in mass concrete structures typically features low water-to-binder ratios and high binder contents, resulting in intense hydration heat evolution and pronounced shrinkage deformation; when coupled with its inherently limited tensile strain capacity, the material is highly susceptible to cracking, thereby compromising long-term structural durability. To actively mitigate shrinkage deformation and reduce cracking risk, high-modulus heat-shrinkable fibers were incorporated into cementitious materials. Their thermal shrinkage behavior and the resulting effects on the mechanical properties and shrinkage performance of mortar were systematically investigated. The results showed that the fibers exhibited a pronounced thermally activated shrinkage response within the temperature range of 50–90 °C, with tensile strength exceeding 600 MPa and elastic modulus greater than 9 GPa. The shrinkage ratio increased significantly with temperature and reached 2.80% at 90 °C, corresponding to a maximum calculated recovery stress of 14.79 MPa. Temperature was identified as the dominant factor governing fiber shrinkage behavior, whereas the influence of initial fiber length was negligible. Incorporation of heat-shrinkable fibers effectively enhanced the overall performance of mortar. An optimum fiber length of 12 mm and volume fraction of 0.3% provided the best balance between strength development and shrinkage reduction. Under these conditions, the 28-day flexural and compressive strengths exceeded 12.5 MPa and 75.0 MPa, respectively, while the 28-day drying shrinkage was reduced by 49.5% in the dosage-screening series and by 54.7% in the independent validation series (233 με); the lowest absolute 28-day shrinkage (220 με) was obtained at 0.5% fiber content, but at the cost of flowability and compressive strength. Under steam curing the fibers were activated further and the mortar reached 13.2 MPa and 77.8 MPa; the same regime did not raise the strength of the plain matrix above its standard-cured value. The significant reduction in drying shrinkage and improved flexural behavior is attributed to the combined effects of fiber bridging and thermally induced shrinkage stress. The contraction of activated fibers is inferred to induce localized pre-compressive effects within the matrix, which can help counteract shrinkage-induced tensile stress, thereby reducing the driving force for early-age microcracking.

Polymers doi: 10.3390/polym18212775

Authors: Fatih Gül Erkan Caner Ozkat Karim El Haloui

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is the most widely used conducting polymer in printed and flexible sensors. It is water-processable, can be made compliant, and conducts holes and ions. Most of these properties, and its drift, respond to one variable, the grain morphology of the film, around which this review is organised. The review first describes PEDOT-rich grains in a PSS matrix and the resulting mixed ionic–electronic transport. It then compares secondary doping, post-treatments, ionic additives, and crosslinkers by their effects on conductivity, stretchability, and aqueous stability. Printing routes, inks, application-specific device stacks, and transduction modes follow. Next, failure mechanisms are mapped onto the sensor classes they dominate. Reversible water uptake, ageing, electrochemical de-doping, cracking, delamination, and loss of skin contact produce different drift signatures and need different corrections. Analytical performance is compared across material classes. As a bare chemiresistor, the polymer works in the parts-per-million decade. As the channel of an electrochemical transistor with a functionalised gate, it reaches nanomolar detection limits. Detection limit, linear range, and interference at a stated humidity are rarely reported together. This review documents that gap. Finally, it describes the calibration steps that recover a measurand from a drifting signal and proposes a minimum reporting set.

Polymers doi: 10.3390/polym18212774

Authors: Jia-Wun Li Chia-Lin Li Jen-Kai Yang Jung-Feng Chang Yu-Heng Liao Chih-Wei Chiu

In this study, high-performance chemical filters were developed by combining surface-modified activated carbon with activated carbon fiber (ACF) nonwoven layers to improve the removal of volatile organic compounds (VOCs) and acidic/basic gases. Activated carbon was modified using ammonium hydroxide, formic acid, and nitric acid, and the resulting pore structure, surface morphology, and functional groups were characterized using BET, FE-SEM, and XPS analyses. AC-NH4OH exhibited a favorable microporous structure and high specific surface area, and exhibited the best adsorption performance toward toluene, isopropyl alcohol (IPA), and acetic acid, whereas AC-HNO3 showed the best performance toward ammonia, possibly associated with changes in its surface functional groups. The modified activated carbon was further incorporated into chemical filters with nonwoven fabrics and adhesive. Because increasing adhesive content reduced adsorption performance through surface coverage and pore blockage, 5 wt% adhesive was selected as the preferred formulation among the adhesive-containing samples investigated. The optimized filters outperformed a commercial chemical filter for all tested gases. The incorporation of ACF provided additional microporous adsorption sites, and a single ACF layer improved the effective removal time for toluene and IPA by approximately 10.5% and 14.7%, respectively. These findings demonstrate the potential of integrating surface-modified activated carbon with ACF nonwoven layers to enhance gaseous pollutant removal for airborne molecular contaminant control in semiconductor manufacturing.

Polymers doi: 10.3390/polym18212773

Authors: Toqeer Ali Syed Ali Alatify Ali Akarma Muhammad Tayyab Naqash Abdulaziz Alqurashi

A utility reclaiming effluent with polymeric membranes must choose a configuration and a deployment coverage. A coverage-aware volume and cost model for an illustrative arid zone of 10Mm3/yr compares ultrafiltration (Configuration A) with ultrafiltration plus polyamide thin-film-composite reverse osmosis (Configuration B). Membrane parameters are literature-derived, eligibility and placement assumed, and no experiments were performed. At 50% coverage and 1 USD/m3, Configuration A avoids 11.5 percentage points of potable input at 0.48 USD/m3 and Configuration B 20.4 points at 0.70 USD/m3, or 0.56 and 0.82 USD/m3 without real-loss credit. Break-even coverages are 11.7% and 11.5%. Configuration B is preferable above a crossover value of 0.98 USD/m3 (1.15 without loss credit) and leads in 46.2% of paired draws at 1 USD/m3. Feed salinity, regulation, concentrate cost, and capital and financing costs move the crossover most. Under independent inputs and assumed eligibility, approved demand rather than recovery limits volume in at least 98.8% of draws, and placement dominates net-benefit variance. Adverse feed conditions that couple operating and cost parameters make treatment costs comparably influential for Configuration B. The thresholds are conditional criteria, not city-specific predictions.

Polymers doi: 10.3390/polym18212771

Authors: Lei Xiong Xuwen Sun Tao Yuan Bing Xiong Yanxiang Mao Haixia Qi Feng Liu

Conventional aromatic polyimides suffer from poor solubility, high water absorption and low visible-light transmittance due to strong interchain charge transfer complex (CTC) interactions, limiting their microelectronic and optoelectronic applications. Here, a novel asymmetric bio-based diamine ENDAP bearing a 3,4,5,6,7,8-hexahydro-2H-2,4a-epoxynaphthalene-3,4-diyl (HEN) alicyclic skeleton was synthesized from menthofuran via a four-step route. ENDAP was polymerized with five commercial dianhydrides to give polyimide films. GPC gave Mn of 3.17–4.68 × 104 and Mw of 4.51–7.94 × 104 Da. These amorphous polyimides, with d-spacings of 4.70–5.49 Å, were mostly soluble in polar aprotic solvents. Water contact angles were 83.3–98.6°, with a minimum water absorption of 0.36% after 48 h. Tg ranged from 164 to 211 °C, the maximum T10 was 451 °C under N2, cutoff wavelengths were 353–388 nm, and maximum T450 of 83.6% and maximum T500 of 86.1%. The HEN skeleton contributes to improved solubility, reduced water absorption and enhanced transparency, likely by weakening CTC interactions and loosening chain packing, as reflected by the enlarged interchain d-spacing, although the extent depends on the dianhydride structure. This work suggests that renewable semi-alicyclic polyimides are potential candidates for microelectronic and optoelectronic applications.

Polymers doi: 10.3390/polym18212772

Authors: Dmitry Igorevich Klimov Rodion Alexandrovich Vinogradov Anastasia A. Semenova Yulia K. Yushina Anzhelika A. Makhova Elena V. Zaiko Maria A. Grudistova Elena A. Zezina Alexey A. Zharikov Alexey A. Zezin

Interpolyelectrolyte complexes (IPEC) of polyethyleneimine (PEI) and polyacrylic acid (PAA) have inherent biocidal activity, high affinity for various surfaces and can be modified with fillers; therefore, they can serve as platforms for developing aqueous antifungal formulations and prospective surface-treatment systems. IPEC dispersions with PEI/PAA molar ratios of 3/1 and 1/3, as well as PEI/PAA-Ag+ complexes, were prepared. UV irradiation of the metal–polymer complexes formed nanoparticles up to 30 nm in PEI-rich and 60 nm in PAA-rich complexes, according to spectroscopy and TEM. Electrophoretic mobility measurements revealed high positive +1.22 ± 0.13 and negative −3.6 ± 0.3 (µm·s−1)/(V·cm−1) values for 3PEI/1PAA and 1PEI/3PAA IPEC, respectively, which can be attributed to the formation of colloidal particles with an external arrangement of charged loops and tails of the excess component. The antifungal activity of the formulations was evaluated against six mold strains in suspension assays. PEI-rich complexes showed limited activity, whereas PAA-rich IPEC was inactive without silver. Incorporation of silver nanoparticles markedly enhanced activity; 1PEI/3PAA-Ag inhibited all tested mold strains in suspension. In biofilm formation assays, its efficacy reached 99% against P. polonicum and 85% against A. wentii, respectively. The 3PEI/1PAA-Ag hybrid showed lower efficacy (42% and 87%). Overall, the composites were more effective against developing than preformed biofilms.

Polymers doi: 10.3390/polym18212769

Authors: Zhanhui Wang Haonan Liu Furen Xiao Haichao Hu Yan Bi

Processing conditions govern the mechanical response of continuous carbon fiber-reinforced polycarbonate (CCF/PC) laminates. This study examined variations in mechanical properties and associated damage in cross-ply laminates using an L9 orthogonal design varying pre-molding temperature, consolidation pressure, and consolidation time. Tensile, flexural, and short-beam tests were combined with descriptive factor-level mean and range analyses, scanning electron microscopy, and post-test computed tomography. The largest observed factor-level range corresponded to temperature for tensile strength, pressure for tensile modulus, and time for flexural properties and apparent interlaminar shear strength (ILSS). All five properties reached their highest time-level mean at 10 min. Among the tested combinations, 210 °C–1.0 MPa–15 min gave the highest mean tensile strength and apparent ILSS (752 and 21.4 MPa), whereas 210 °C–2.0 MPa–10 min gave the highest tensile modulus, flexural strength, and flexural modulus (61.5 GPa, 720 MPa, and 67.5 GPa). Representative tensile fracture surfaces associated higher specimen strength with matrix attachment and tearing, and lower specimen strength with interfacial separation. Flexural specimens exhibited compression-side damage and delamination. These findings distinguish property-specific processing responses and show that interpreting flexural performance requires consideration of both compression-side and interlaminar damage.

Polymers doi: 10.3390/polym18212770

Authors: Royal Guliyev Nalan Tekin Mustafa Özgür Bora Yavuz Emre Yağci Aygun Isayeva

Replacing petroleum-based polyols with renewable feedstocks is essential for sustainable polyurethane (PU) production. In this study, an eco-friendly bio-polyol was synthesized using chitosan, glycerine, and PEG-400 to prepare semi-rigid bio-based PU foams at 50%, 75%, and 100% substitution ratios. The chemical, morphological, mechanical, and thermal properties were systematically evaluated. FTIR confirmed successful bio-polyol integration, while SEM revealed refined cell-dimensions and enhanced structural homogeneity. Although the apparent density decreased from 0.0835 g/cm3 to 0.0657 g/cm3, the bio-based foams exhibited superior water resistance and mechanical performance with the 75% substituted formulation (75 Bio PU). To justify field performance under demanding operational environments (e.g., building envelopes under solar heat load and hot pipeline insulation), the thermal conductivity was evaluated at 100 °C, maintaining efficient insulation (0.044–0.047 W m−1 K−1). TGA/DTG analysis demonstrated that while bio-polyol incorporation lowered the initial decomposition temperatures, 75 Bio PU enhanced the thermal resistance (T %max = 408 °C) and char residue (15.68%), underscoring superior high-temperature carbonization. UL-94 tests indicated the need for supplementary flame-retardants. Overall, the 75 Bio PU formulation provides optimal balanced performance for sustainable building insulation, industrial heat shielding, and automotive interior components.

Polymers doi: 10.3390/polym18212768

Authors: Damian Bodniewicz Mirosław Bocian

This study presents a finite element framework for injection-molded short-fiber-reinforced thermoplastics that accounts for process-induced anisotropy, temperature, and moisture. A fully oriented material model was combined with fiber orientation tensors from injection-molding simulations to determine local orthotropic thermomechanical properties of PA66-GF30. The model employs micromechanical formulations for elasticity, strength, and thermal expansion. Matrix Young’s modulus, Poisson’s ratio, tensile strength, and coefficient of linear thermal expansion were identified simultaneously through inverse calibration using standardized composite data. Before calibration, prediction accuracy depended strongly on property, temperature, and moisture condition, with the largest deviations occurring at 120 °C and for conditioned-state tensile strength. After calibration, the directly targeted longitudinal Young’s modulus and tensile strength agreed with their targets within ±0.4%. The non-targeted transverse modulus and tensile strength agreed with auxiliary estimates within ±5.4% and ±1.9%, respectively. For the dry-as-molded state, the directional thermal expansion coefficients agreed with their calibration targets within ±5.2%. For the conditioned state, dry-as-molded thermal expansion values were adopted as targets, and deviations remained within ±5.9%. These results demonstrate successful calibration and internal consistency, while independent validation requires directional measurements not used during identification. The framework enables practical mapping of environment-dependent anisotropic properties in structural finite element analysis.

Polymers doi: 10.3390/polym18212767

Authors: Wenjuan Chen Hui Lv Xiaoyan Zhang Jun Zhang

Polypseudorotaxane-based polymeric networks provide a versatile framework for constructing injectable hydrogels with dynamic assembly and multifunctional therapeutic capabilities. Herein, we developed an injectable nanocomposite hydrogel (IA@PFHA) based on a polypseudorotaxane network formed through host–guest assembly of α-cyclodextrin-modified hyaluronic acid (HA-αCD) and indocyanine green (ICG)-loaded Pluronic F127 nanoparticles (ICG@PF127), with 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) incorporated as an oxygen-independent radical initiator. The resulting network enabled the co-incorporation of ICG and AIPH while exhibiting shear-thinning injectability, providing a polymeric platform for localized integration of photothermal and radical-generating functions. Upon 808 nm irradiation, IA@PFHA generated mild hyperthermia below 45 °C while promoting AIPH-derived radical generation. This design integrates mild photothermal therapy (m-PTT) with oxygen-independent thermodynamic therapy (TDT), thereby addressing the limited thermal stress of mild heating and the therapeutic constraints associated with hypoxic tumor microenvironments. In vitro, IA@PFHA retained its radical-generating capability under hypoxic conditions and enhanced NIR-induced cytotoxicity against CAL 27 cells. In vivo, IA@PFHA combined with NIR irradiation achieved greater tumor growth inhibition than the AIPH-free hydrogel and free formulation, despite comparable photothermal responses among ICG-containing groups. Overall, this study demonstrates a polypseudorotaxane-based polymeric hydrogel platform that integrates complementary photothermal and oxygen-independent radical-generating functions within an injectable network, highlighting the potential of dynamic polymeric network design for localized combination therapy for OSCC.

Polymers doi: 10.3390/polym18212766

Authors: Delang Lin Wei Zhong Yayi Chen Ming Li

Thin piezoelectric polymers provide a compliant route for converting transient biomechanical deformation into electrical signals, but wearable sensing also depends on how these high impedance signals are coupled to the electronic readout. This work presents a hybrid sensing platform that combines a piezoelectric film, an InSnZnO (ITZO) dual-gate thin-film transistor (DGTFT), and analog signal conditioning for dynamic force measurement and anterior neck motion sensing. The polymer film contains identifiable electroactive crystalline features and generates repeatable bipolar responses under cyclic loading. The coupled device exhibits gate-dependent drain current responses, while the complete readout provides a force-to-voltage sensitivity of 4.0 V/N over 0.5–1 N. Under continuous 0.5 N cyclic loading for 200 s, the output shows a 3.12% coefficient of variation and a 102.27% final-to-initial response ratio. Neck-mounted measurements further resolve different temporal signatures associated with coughing, swallowing, and pronunciation of “hello”. The results demonstrate a compact polymer-transistor sensing architecture that preserves dynamic mechanical information from controlled loading to wearable biomechanical acquisition.

Polymers doi: 10.3390/polym18212765

Authors: Hoik Lee

Electrospinning cellulose and its derivatives commonly relies on hazardous solvents, motivating the development of less hazardous alternatives. This narrative review examines conventional and alternative solvent systems, relating polymer solubility, processing conditions, and reported fiber morphology to solvent hazards and practical limitations. Representative studies were identified through targeted searches and reference tracking. For cellulose derivatives, aqueous mixtures of acetone, acetic acid, or ethanol and dimethyl carbonate-based formulations provide alternatives to systems containing hazardous amides or chlorinated solvents. For native cellulose, the reviewed routes include N-methylmorpholine N-oxide, aqueous alkali, ionic liquids, and a switchable solvent system based on 1,8-diazabicyclo[5.4.0]undec-7-ene, carbon dioxide, and dimethyl sulfoxide. Reported mean diameters span 160–1280 nm for cellulose acetate in acetic acid/water and 250–750 nm for cellulose in N-methylmorpholine N-oxide/water. These ranges overlap those obtained with conventional systems, but differences in polymer grade and spinning conditions prevent direct performance comparisons. Lower solvent hazard does not establish lower overall environmental impact: heating, coagulation, washing, carrier polymers, and solvent recovery can introduce additional burdens. The available evidence supports several candidate substitutions, while matched-condition comparisons and quantitative measurements of energy use, recovery yield, waste generation, and productivity are needed to establish their suitability for wider application.

Polymers doi: 10.3390/polym18212764

Authors: Arulkumar Nagappan Mahenthiran Ramasamy Radha Arulkumar Arvind Kumar Shukla Sethuraman Veeran

The worldwide shift toward sustainable food systems demands packaging solutions that are compatible with the environment, food safety and shelf-life extension. Phytochemical-functionalized smart polymer films have emerged as promising multifunctional active packaging systems with antioxidant and antimicrobial properties. This review critically examines the molecular mechanisms, fabrication strategies, structure-release-performance relationships, applications, and translational challenges of phytochemical-based smart polymer films. Recent advances in incorporating polyphenols, essential oils, curcuminoids, tocopherols, and related bioactives into polysaccharide-, protein-, and bio-based polyester matrices through direct blending, encapsulation, cyclodextrin inclusion, electrospinning, and hybrid nanoparticle systems are evaluated. Phytochemicals can scavenge reactive oxygen species, chelate pro-oxidant metals, and interrupt radical chain reactions, while smart systems enable controlled or stimuli-responsive release triggered by pH, humidity, temperature, or spoilage volatiles. These designs influence antioxidant and antimicrobial activity, oxygen and water-vapor barrier properties, UV protection, and mechanical performance. Applications across meat, fish, dairy, fruits, vegetables, and high-fat foods demonstrate potential for delaying oxidation, suppressing microbial growth, and maintaining sensory and nutritional quality. This review synthesizes phytochemical–matrix–processing–release–performance relationships into a qualitative, application-oriented design framework, emphasizing measurable parameters, formulation-selection criteria, and validation in the intended food and storage environment.

Polymers doi: 10.3390/polym18212763

Authors: Jiahui Zhang Xiao Wu Shengze Gong Xia Yang Hongbo Li Zebing Xing Yu Xian

In this study, poplar wood flour was modified with alkyl ketene dimer (AKD), and poplar wood flour/polylactic acid (PLA) composites with 0–5% AKD were prepared. Effects of AKD content on wettability, water absorption kinetics, dimensional stability, flexural properties, and microscopic interface were investigated. AKD likely consumed hydroxyl groups through esterification and/or hydrogen bonding, as reported in the literature, and introduced hydrophobic alkyl chains. The 5% AKD sample exhibited the highest contact angle, while the 3% AKD sample showed the lowest total surface free energy (24.73 mJ·m−2). AKD content significantly changed the water diffusion mode: at 0–3% AKD, water absorption followed non-Fickian diffusion, with 2% AKD showing the highest n value (0.7132), indicating swelling-controlled diffusion and the lowest apparent saturation water absorption. At 4% AKD, n decreased to 0.4786, approaching Fickian diffusion, and agglomerated pores accelerated water transport. The 2% AKD sample exhibited optimal interfacial bonding and the highest flexural strength retention (46.29%). The 5% AKD sample showed the lowest steady-state thickness swelling coefficient (10.03%), indicating the best dimensional stability, but agglomeration defects weakened mechanical properties. Interfacial bonding strength, rather than low water absorption or low swelling, was key to mechanical retention. An optimal AKD content range exists when “optimal” is defined by the balance between mechanical retention and dimensional stability: 2% AKD is preferred for mechanical retention, while 5% AKD is preferred for dimensional stability under humid service scenarios. These findings support the water-resistant modification of PLA-based wood–plastic composites.

Polymers doi: 10.3390/polym18212762

Authors: Mohammad H. Alrefeai Fahad Alkhudhairy

To evaluate and compare the effect of different final post space treatments, i.e., methylene blue-mediated antimicrobial photodynamic therapy (aPDT-MB), superparamagnetic iron oxide nanoparticles (SPIONs), and apple cider vinegar (ACV), against the established benchmark of 17% EDTA on smear layer (SL) removal and push-out bond strength (PBS) of glass fiber posts (GFPs) bonded to post space dentin. Endodontic treatment was conducted on eighty human mandibular premolars with single roots, which were obturated. Post spaces were uniformly prepared, and specimens were randomly divided into four groups based on the final post space treatment protocol (n = 20 per group): Group 1 (NaOCl + 17% EDTA), Group 2 (NaOCl + aPDT-MB), Group 3 (NaOCl+ SPIONs), and Group 4 (NaOCl + ACV). All teeth received conventional root canal treatment, including a final 17% EDTA rinse, before post-space preparation. Within each group, ten teeth were allocated to SL evaluation by scanning electron microscopy (SEM) and ten to PBS testing, in which GFPs were luted with a dual-cure self-adhesive resin cement. The two outcomes were therefore measured in different teeth, and antimicrobial efficacy was not assessed. The teeth underwent thermocycling (10,000 cycles, 5–60 °C) and were sectioned into cervical, middle, and apical segments. These segments were subjected to PBS testing at a speed of 0.5 mm/min using a universal testing machine (n = 10), and failure modes were determined through stereomicroscopic analysis. PBS data were analyzed using a two-way mixed ANOVA followed by simple-effects analyses with Tukey- and Bonferroni-adjusted comparisons; ordinal SL scores were analyzed using Kruskal–Wallis (between protocols) and Friedman (between root thirds) tests with Bonferroni-adjusted pairwise comparisons (α = 0.05). Group 3 (NaOCl + SPIONs) showed the lowest SL scores (medians 1.20–1.32) and the highest PBS values (10.70 ± 0.76 to 11.20 ± 0.84 MPa; maximum at the cervical third). Group 2 (NaOCl + aPDT-MB) showed the highest SL scores (medians 2.60–3.54) and the lowest bond strength (3.90 ± 0.52 to 6.10 ± 0.58 MPa). PBS ranged from 7.20 to 10.90 MPa in Group 1 and from 6.10 to 7.90 MPa in Group 4. No statistically significant difference was detected between NaOCl + EDTA and NaOCl + SPIONs at the cervical and middle thirds, whereas at the apical third NaOCl + SPIONs showed lower SL scores and higher PBS (mean difference 3.50 MPa; 95% CI 2.75–4.25). Combined NaOCl and SPIONs irrigation did not differ significantly from NaOCl + EDTA in the cervical and middle thirds and outperformed it in the apical third; this promising approach requires further validation, including assessment of residual nanoparticles, biological safety, and long-term bond durability.

Polymers doi: 10.3390/polym18212761

Authors: Mónica Alejandra Carrazco-Rivera Laura Leticia Barrera-Necha José Luis Trejo-Espino Pedro Lina-Manjarrez Jaime Lizardi-Mendoza Karla Guadalupe Martínez-Robinson Victor Manuel Orozco-Carmona José Luis Acosta-Rodríguez

Chitosan films are promising materials for food-related applications, but their performance depends on polymer characteristics. This study compared films from hybrid chemical–microbiological shrimp (CM-Shr) and crab (CM-Crb) chitosans, chemically extracted crab chitosan (Ch-Crb), and high- (Ref-H) and low-molecular-weight (Ref-L) reference chitosans. Films were prepared using 1.5% (w/v) chitosan in 1% (v/v) acetic acid with glycerol at 30% (w/w, relative to dry chitosan). Chitosans were characterized by degree of deacetylation, molecular weight, moisture, ash, nitrogen and ATR-FTIR; films were assessed for thermal, morphological, hydration, mechanical, optical, and antibacterial properties. ATR-FTIR indicated differences in amino, residual N-acetyl, and hydrogen-bonded environments. At 15 min, CM-Crb and Ch-Crb exhibited lower apparent water absorption (34.5 ± 1.2% and 32.6 ± 0.7%) than Ref-H (51.8 ± 1.9%). Antibacterial inhibition beyond the 6 mm film-disk diameter was absent at 1.5% and predominantly detected for CM-Crb and Ch-Crb at 3.0–4.5% (w/v) chitosan in the film-forming solutions. CM-Crb exhibited tensile strength of 52.1 ± 4.3 MPa, the highest elongation at break (3.7 ± 0.3%) and UV blocking at 340 nm (35%). Film performance was associated with the physicochemical profiles and processing history of the starting chitosans.

Polymers doi: 10.3390/polym18212760

Authors: Caterine Donoso Gabriela Taipe-Andagua Liliana Guzmán-Beckmann Alberto Coronas Alexis Debut Sebastian Taco-Vasquez Lucia E. Manangon-Perugachi Andrés Chico-Proaño Joan Carles Bruno

Post-consumer polypropylene (PP) waste is a growing environmental liability in developing economies with limited recycling infrastructure. This study presents an integrated kinetic-to-reactor approach for the catalytic pyrolysis of three compositionally distinct post-consumer PP streams, combining a moderate vacuum (0.45 bar absolute) with a regenerated fluid catalytic cracking (FCC) catalyst to produce diesel-range fuel while valorising two industrial waste streams. The activation energies derived from thermogravimetric analysis (β = 30 °C min−1, N2) using the Coats–Redfern method were 178.3 kJ mol−1 for the near-pure isotactic PP feedstock, consistent with random chain scission, and 209.2 and 351.9 kJ mol−1 for the UV-stabilised and PP/HDPE streams, respectively, reflecting the feedstock composition; the DTG profile informed the selection of 450 °C as the reactor set point. At the best condition within the studied domain (Cat/PP = 0.03 g g−1, 2 h, 450 °C), the regenerated FCC catalyst achieved 75.10 wt% liquid yield, a 50% improvement over thermal pyrolysis, with a low aromatic content of 1.69 area%,attributed primarily to the moderate acidity of the regenerated catalyst, versus the 10–25 wt% typical of atmospheric zeolitic pyrolysis. Vacuum distillation yielded a diesel fraction that mainly complies with the ASTM D975 Grade 2-D S15 parameters (cetane index 68.92, sulphur 14.1 ppm) without hydrotreatment, demonstrating a technically viable waste-to-fuel pathway where post-consumer polyolefins and refinery FCC by-products are simultaneously abundant.

Polymers doi: 10.3390/polym18212759

Authors: Caroline Beatriz de Oliveira Nara Cristina de Souza Paula Becker Pertuzatti Konda Ricardo Stefani

Antioxidant active packaging delays lipid oxidation by transferring a bioactive compound from the polymer to the food, so the rate of that transfer is the property that matters. Poly(vinyl alcohol) (PVA) is a biodegradable, non-toxic film-former, but how its molecular weight governs polyphenol release has not been resolved. Films were cast from PVA of low (31–50 kDa), medium (85–124 kDa) and high (146–186 kDa) molecular weight in four formulations: unloaded (F1), quercetin pre-dissolved in ethanol at 0.5 (F2) and 1.0 g L−1 (F3), and quercetin added as a powder at 1.0 g L−1 (F4). The FT-IR of all four formulations showed the crystalline quercetin band set, led by the aromatic C=C mode at 1520 cm−1, only in F4; F3 carried the same loading and showed none of it, so the method of incorporation rather than the loading decides whether a crystalline quercetin phase forms. The X-ray diffraction of all four formulations confirmed a separate crystalline phase in F4 alone: the mean height of the four diagnostic quercetin reflections was 0.013–0.033 relative to the PVA (101) reflection in F1, F2 and F3 and 0.931 in F4, with the 12.54° reflection reaching 2.59–2.89 times the polymer reflection. Atomic force microscopy found both 1.0 g L−1 formulations rougher than the control at every molecular weight, regardless of whether a crystalline phase was present, so surface relief at this loading did not report crystallinity; the two differed in roughness from each other as much as from the control, so the method of incorporation affect topography as well. The antioxidant assays add the functional consequence of the structural difference: in the fatty-food simulant, the only medium in which quercetin was freely soluble, the dispersed form yielded 1.8 times the DPPH activity and 2.1 times the extractable phenolic content of the crystalline form at the same loading, while in the two aqueous simulants, they were indistinguishable. Quercetin release in PBS over 12 days, analysed as a mixed-effects model with a random intercept for each of the 26 specimens, was governed by a molecular weight × formulation interaction (χ2=31.8 on 4 d.f., p<0.0001) with neither main effect significant alone. F3 and F4 released statistically identical total amounts (28.4 and 29.2 μmol g−1, p=0.72) but in opposite molecular-weight orders (F(2,11)=6.61, p=0.013): the non-crystalline form released 15.9 μmol g−1 more from the low-molecular-weight matrix, the crystalline form 13.8 μmol g−1 more from the high-molecular-weight one. Across ABTS, DPPH and Folin–Ciocalteu assays, the extractable antioxidant was governed chiefly by the simulant, decreasing as ethanol 95% > ethanol 10% > acetic acid 3%, consistent with the poor aqueous solubility of quercetin, and was highest from the low-molecular-weight films in all three assays. Surface roughness also fell with molecular weight from Sq=114.9 to 30.3 nm in the unloaded films. The practical conclusion is that quercetin loading and the method of its incorporation must be chosen together with the polymer grade, because the incorporation method determines which molecular weight releases fastest.

Polymers doi: 10.3390/polym18212758

Authors: Dunyansed Sarine Borges-Palomo Carlos Rolando Ríos-Soberanis Roberto Carlos Anaya-Ramírez Alejandro Ortiz-Fernández Emilio Pérez-Pacheco

The durability of fiber-reinforced epoxy composites in marine environments depends on the interaction among interfacial characteristics, moisture transport, and damage evolution. However, it remains poorly understood whether E-CR/PP hybridization merely provides a secondary reinforcing phase or also modifies moisture-transport and load-transfer mechanisms. This study investigated the effects of incorporating E-CR glass fibers and polypropylene (PP) fibers on moisture absorption, mechanical response, and damage development in an epoxy matrix. The reinforced composites were subjected to short-term seawater immersion for up to 30 days. FTIR-ATR, AFM, micromechanical testing, moisture absorption and diffusion analysis, flexural testing, and acoustic emission were combined to relate surface characteristics and interfacial behavior to moisture transport and mechanical performance. The neat epoxy matrix showed progressive moisture uptake and a 22.03% reduction in acoustic-wave propagation velocity, consistent with moisture-induced plasticization and reduced effective stiffness. The incorporation of 5 wt.% PP was associated with lower moisture uptake in composites containing equivalent E-CR contents and with a reduction in the estimated effective diffusion coefficient. The CPPV formulation, containing 50 wt.% E-CR and 5 wt.% PP, exhibited the lowest measured moisture uptake (1.20%) and effective diffusion coefficient (2.96 × 10−12 m2 s−1) among the formulations investigated during the early immersion period. After 30 days of seawater immersion, CPPV exhibited a residual flexural strength of approximately 600 MPa, compared with approximately 420 MPa for the corresponding 50 wt.% E-CR composite without PP (CFV). These findings indicate that PP does not act solely as a secondary reinforcing phase; rather, E-CR/PP hybridization modifies the effective moisture-transport environment and load-transfer response of the epoxy composite. Within the 30-day exposure period investigated, the hybrid architecture therefore provided improved resistance to moisture ingress and higher residual flexural strength. Longer-term exposure studies are required to establish whether these advantages persist under prolonged marine aging.

Polymers doi: 10.3390/polym18212757

Authors: Alihan Cambaz Huseyin Enes Salman

On-site repair of carbon fibre-reinforced polymer (CFRP) structures is widely employed when component removal and autoclave-based processing are impractical. However, existing repair guidelines provide limited guidance on the interaction between closely spaced repairs. The objective of this research is to investigate the coupled effects of ligament spacing, patch lay-up, and repair arrangement on the residual tensile strength of dual stepped-lap repaired composite panels. The methodology consists of a shell-based finite element model combining Hashin intralaminar damage and a mixed-mode bilinear cohesive zone model, which was validated against published experiments on damaged, stepped, and wet lay-up repaired laminates, predicting the measured strengths within 6.4%. Subsequently, fifteen repair configurations were analyzed, comprising four ligament spacings, three patch lay-up strategies, and two repair arrangements. Residual strength varied non-monotonically with ligament spacing for repairs arranged transverse to the loading direction. For the baseline patch, the strength retention factor increased from 0.57 for closely spaced repairs to a maximum of 0.85 at 120 mm, and decreased to 0.59 at 180 mm as the repairs approached the panel free edges. The compliant ±45° patch was the most sensitive to spacing (0.42–0.80), whereas the stiffness-matched patch varied only between 0.48 and 0.61. In contrast, in-line repairs showed limited sensitivity to spacing, retaining 0.72–0.77 of the intact strength. In conclusion, the results demonstrate that repair orientation relative to the principal load path governs the interaction between adjacent repairs more strongly than separation distance alone.

Polymers doi: 10.3390/polym18212755

Authors: Farah Elfakhri Giles McCracken Matthew German Rawan N. AlKahtani

The study investigates the effects of acidic, neutral, and alkaline environments on the micro- and nanoscale properties of experimental BisGMA/TEGDMA resin composites with varied filler loading. Experimental composites based on BisGMA:TEGDMA at 75:25 wt% with three silica-glass filler loadings (75, 40, and 0 wt%) were stored at 37 °C in phosphate-buffered saline (PBS; pH 7.2), citric acid (pH 3.8), or sodium hydroxide (NaOH; pH 11) for up to 28 days. Microscale changes were assessed using sorption, Vickers hardness, and scanning electron microscopy (SEM), while atomic force microscopy (AFM) was used to evaluate nanoscale surface roughness and Young’s modulus. Storage medium did not significantly affect percentage mass increase (p = 0.092) or Vickers hardness (p = 0.098). Higher filler loading was associated with lower mass increase (ρ = −0.902, p < 0.001) and greater hardness (r = 0.660, p < 0.0001). SEM revealed surface degradation, particularly at the filler–matrix interface following NaOH exposure. Nanoscale surface roughness was negatively associated with filler loading (ρ = −0.368, p = 0.001), with changes observed predominantly in unfilled materials after 28 days. AFM measurements demonstrated a shift towards lower Young’s modulus values after only one day of exposure to citric acid and NaOH, whereas the reduction in PBS occurred later. Acidic and alkaline exposure produced limited alterations in conventional microscale measures but more changes in surface morphology and nanoscale properties. These exploratory findings suggest that AFM-derived Young’s modulus may detect early softening following acidic and alkaline exposure, suggesting its potential utility for characterizing early changes associated with chemical ageing than conventional microscale measurements.

Polymers doi: 10.3390/polym18212756

Authors: Alessia Pantaleoni Baljinder K. Kandola A. Richard Horrocks Irene Bavasso Maria Paola Bracciale Erika Palazzi Carlos A. Fuentes Khouloud Tilouche-Guerdelli Jacopo Tirillò Assunta Marrocchi Fabrizio Sarasini

This work has investigated epoxy composites reinforced with wool fabrics modified by an organosolv lignin coating deposited via a sustainable protocol. The lignin layer was introduced to tailor the fiber/matrix interphase, aiming to improve adhesion and reduce water-related degradation associated with the intrinsic hygroscopicity of wool. Laminates were manufactured by vacuum-assisted resin transfer molding (VARTM) and systematically characterized. Thermogravimetric analysis demonstrated improved thermal stability and higher char yield in lignin-coated composites. Mechanical tests revealed enhanced flexural strength (+21%) and modulus (+31%), together with a modest increase in interlaminar shear strength. SEM analysis of the fracture surfaces provided additional evidence of changes in fiber–matrix interfacial interactions. Low-velocity impact and DMA results further supported the role of the coating in improving load transfer and viscoelastic response. Water absorption tests indicated reduced equilibrium uptake and slower diffusion kinetics, highlighting the hydrophobic barrier function of the lignin layer. Collectively, these results show that the lignin coating acts primarily as an interphase modifier and water-barrier layer, enabling low-value wool fabrics to be upgraded into functional reinforcements for more durable epoxy biocomposites.

Polymers doi: 10.3390/polym18212753

Authors: Yunqin Qi Zhouyang Xiang Qingyi Lin Zhenhua Hu

The development of renewable fluorescent nanomaterials for heavy-metal detection provides an opportunity to integrate biomass valorization with functional sensing. Herein, N,S-codoped carbon quantum dots (N,S-CQDs) were prepared by one-step hydrothermal co-carbonization of bagasse-derived xylan, a renewable and hydroxyl-rich hemicellulose selected as the carbon precursor, and L-cysteine. The quasi-spherical N,S-CQDs had a mean diameter of 3.25 ± 0.04 nm and exhibited locally ordered carbon domains and abundant N-, S-, and O-containing surface functionalities. They exhibited excitation-dependent blue fluorescence with optimal excitation/emission wavelengths of 330/420 nm and a relative fluorescence quantum yield of 67.25%. Among the tested metal ions, Hg2+ caused the strongest fluorescence quenching, with a concentration-dependent response over 0–1.0 μM and a detection limit of 4.2 nM. Spectroscopic changes and fluorescence recovery after Ethylenediaminetetraacetic acid (EDTA) treatment were consistent with reversible interactions between Hg2+ and surface functional groups. Immobilization on filter paper yielded a visually responsive Hg2+ sensor with a fluorescence-based detection limit of 6.23 μM and reversible quenching-recovery behavior during repeated Hg2+/EDTA treatments. This work integrates renewable xylan valorization, heteroatom-doped carbon dot synthesis, and Hg2+-responsive fluorescence, broadening the functional utilization of hemicellulosic resources in portable heavy-metal sensing and providing a design strategy for biomass-derived fluorescent carbon materials for environmental detection.

Polymers doi: 10.3390/polym18212754

Authors: Yao Zhu Xue Liu Wei Zhong Jiwen Fang Chong Li Xiaohong Dong Jiang Shao

Wind energy is one of the most abundant and sustainable renewable energy resources. However, its efficient utilization remains challenging because of fluctuating wind speeds and multidirectional airflow. In this work, we develop a dual-rotor hybrid triboelectric–electromagnetic energy harvester (H-TENG) featuring flexible multiwalled carbon nanotube/poly(dimethylsiloxane) (MWCNTs/PDMS) composite electrodes to improve wind energy harvesting efficiency. The effects of electrode materials and rotor configurations on the electrical output of the device are systematically investigated. Compared with conventional copper electrodes, the flexible MWCNTs/PDMS composite electrodes increase the peak output power of the triboelectric unit by 46.1% at a wind speed of 6 m s−1, while the dual-rotor configuration further enhances the peak output power by up to approximately 195.6% relative to the single-rotor design. To overcome the limited, short-circuit current output of the triboelectric generator, an electromagnetic generator is integrated into the hybrid system. The optimized device delivers a maximum output open-circuit voltage of 1212.34 V from the TENG and a maximum short-circuit current of 13.64 mA from the EMG. The harvested energy is sufficient to continuously power a digital watch and 240 light-emitting diodes (LEDs). This work provides an effective material–structure synergistic strategy for high-performance hybrid wind energy harvesters and offers a promising approach for harvesting low-speed and multidirectional wind energy.

Polymers doi: 10.3390/polym18212752

Authors: Kenan Tüfekci

Thermoplastic polyurethane (TPU) filaments are increasingly used in additively manufactured structures that require large deformation and flexible mechanical response. In this study, the mechanical behavior of TPU-95A filament was experimentally characterized and implemented in finite element analyses of lattice-structured airless tire prototypes. Tensile tests were conducted at three different loading rates using a custom-made desktop testing device, and the resulting stress–strain curves were used to calibrate the PolyUMod Three Network Model (TNM) in Ansys MCalibration version 25.1. Four airless tire prototypes were then designed, comprising a conventional hexagonal lattice and three lattice configurations based on auxetic unit-cell geometries: reentrant, arrowhead, and star. The prototypes were fabricated using fused deposition modeling and subjected to compression tests to characterize their force–displacement responses. Comparison with compression experiments at a single loading rate showed geometry-dependent agreement for the four investigated lattice configurations, supporting the applicability of the filament-derived TNM parameters under the tested conditions. Numerical predictions were validated against experimental force–displacement curves using the normalized root mean square error (NRMSE). The NRMSE values were 8.23%, 11.89%, 17.61%, and 3.94% for the hexagonal, reentrant, arrowhead, and star structures, respectively. Overall, the results demonstrate the capability of the calibrated TNM-based finite element approach to predict the compression behavior of additively manufactured TPU-95A lattice structures.

Polymers doi: 10.3390/polym18212750

Authors: Gianluca Ciarleglio Maria Gabriella Santonicola

Electrospun nanofibers provide high surface area, interconnected porosity, and extracellular-matrix-like architectures that can be combined with controlled degradation, local therapeutic delivery, and surface biofunctionalization. This review examines bioactive electrospun materials from a materials-design perspective, focusing on the relationships among polymer selection, electrospinning conditions, fiber architecture, bioactive-agent localization, and application-specific performance. Synthetic biodegradable polymers, natural and bio-derived polymers, and hybrid systems are discussed together with random, aligned, multilayer, and core–shell architectures. Bioactivation strategies include direct incorporation of therapeutic agents or functional nanophases, core–shell localization for payload protection and release control, surface functionalization, endogenous-factor recruitment, and stimulus-responsive activation. Three biomedical interfaces are considered as contrasting application models: wound dressings, urological repair, and implant or biomedical-device coatings. Their comparison highlights distinct requirements related to hydration, mechanical loading, microbial exposure, tissue interaction, coating–substrate integrity, and functional lifetime. Particular attention is given to wet-state stability, preservation of bioactive function, sterilization, manufacturing reproducibility, and validation against application-specific failure modes. Overall, the assessment of electrospun biomedical materials should extend beyond as-fabricated morphology and bioactive-agent incorporation to establish whether structural, interfacial, and biological functions are retained under application-relevant conditions.

Polymers doi: 10.3390/polym18212751

Authors: Yuli Nurul Maulida Ellana Nabilah Nur Averina Ansar Merreta Noorenza Biutty PilHo Huh Seong Il Yoo

Recently, the development of biomass-based polymers has attracted a great deal of attention as a sustainable alternative to petroleum-based plastics. However, the relatively limited mechanical properties of these bio-derived polymers often require reinforcement through the inclusion of nanofillers, while the environmental durability of such nanocomposites remains insufficiently understood. In this regard, we prepared nanocomposites composed of isosorbide-based polycarbonate (ISB-PC) and surface-modified cellulose nanocrystals (CNCs), and examined the effect of nanofillers on the mechanical properties and their retention under humid soil exposure. Interestingly, the initial reinforcement effect provided by CNCs rapidly decreased during the early stage of exposure, and the mechanical properties of the ISB-PC composites eventually converged toward those of pristine ISB-PC within a relatively short time. Based on the time-dependent changes in mechanical properties and mass loss, we propose that the mechanical deterioration was associated with physical changes in the polymer matrix, accompanied by the formation of macroscale cavities within the films. Our results suggest that initial reinforcement does not necessarily ensure sustained mechanical performance under humid soil exposure.

Polymers doi: 10.3390/polym18212749

Authors: C. J. Martel-Benítez R. Henríquez-Cabrera R. Alayón-Afonso D. Padilla F. Real A. Martel-Quintana J. L. Gómez-Pinchetti C. Almeida P. Santiago-Díaz N. Robles-Antón N. González-Caballero J. L. Martín-Barrasa

Microbial exopolysaccharides (EPSs) are functional biopolymers of growing scientific and industrial interest because of their structural diversity, biocompatibility, and rheological properties. Microbial β-(1→3)-glucans are of particular biological and technological interest, and their production depends strongly on strain characteristics, medium composition, and culture conditions. This study characterized the temporal relationship among bacterial growth, viability, and aniline-blue reactivity in Alcaligenes faecalis A12C under batch growth and fermentation conditions. Growth turbidity, viable bacterial concentration, and β-(1→3)-glucan-associated signals were monitored over 96 h using spectrophotometric, microbiological, and microscopic approaches. In growth culture medium (GCM), OD600 increased after 24–30 h and reached approximately 2.4 at 72 h, coinciding with the highest viable count (2.44 × 1021 CFU/mL). Aniline-blue coloration became clearly detectable after 30 h and persisted through 96 h, when microscopy showed blue staining associated with bacterial cells. In fermentation culture medium (FCM), OD600 increased progressively to approximately 2.8 at 96 h, whereas viable counts followed a distinct temporal profile. Aniline-blue reactivity changed during the first 24 h and remained close to an A610 of approximately 1.0 thereafter. These findings indicate distinct temporal patterns among culture turbidity, viability, and aniline-blue reactivity and provide a framework for subsequent structural characterization of the detected material.

Polymers doi: 10.3390/polym18212748

Authors: Silvia Rojas-Rueda Fabio Luiz Andretti Carlos A. Jurado Rene Garcia-Contreras Jose Vivaldi Abdullah Almansour Hamad Algamaiah Abdulrahman Alshabib

Background: This in vitro study compared the effects of four commercial hydrofluoric acid etchants with different nominal concentrations on the surface roughness of a 3D-printed lithium disilicate-filled polymer resin, evaluated after post-polymerization without debinding or sintering. Methods: Seventy-five specimens were randomly assigned to five groups (n = 15): G1, 4.5% hydrofluoric acid (IPS Ceramic Etching Gel, Ivoclar); G2, 4% hydrofluoric acid (Porcelain Etchant, Bisco); G3, 9.5% hydrofluoric acid (Porcelain Etchant, Bisco); G4, 9% hydrofluoric acid (Porcelain Etch, Ultradent); and G5, an unetched control. Etchants were applied for 20 s. Areal surface roughness (Sa) was measured using non-contact optical profilometry. Data were analyzed using Levene’s test, conventional and Welch’s analyses of variance, and Games–Howell pairwise comparisons (α = 0.05). Results: Both analyses of variance identified significant differences among groups (p < 0.001). All pairwise comparisons were statistically significant (p < 0.001). Mean Sa values were 0.1558 ± 0.0159 µm for G5, 0.3159 ± 0.0313 µm for G1, 0.5093 ± 0.0467 µm for G2, 0.7243 ± 0.0409 µm for G3, and 0.9365 ± 0.0408 µm for G4. The 9% Ultradent etchant produced the greatest roughness, approximately six times the control value. Conclusions: All etchants significantly increased surface roughness. However, the ranking did not follow nominal acid concentration, and differences in commercial formulations prevent attribution of the observed effects to concentration alone. These findings characterize surface modification of a 3D-printed lithium disilicate-filled polymer resin and should not be generalized to conventional lithium disilicate ceramics. Further studies are needed to determine whether these topographic changes improve subsequent adhesive bond strength or long-term durability.

Polymers doi: 10.3390/polym18212747

Authors: Andrei Călin Georgiana Ionela Păduraru Delia Alexandra Prisecaru Lucian Cucu Marilena Stoica

3D-printed polymers and polymer composites are increasingly used in sliding and abrasive contacts, but their friction and wear cannot be transferred directly from data for moulded polymers, because printing creates layered interfaces, process-specific surface textures and position-dependent crystallinity. This systematised critical review analyses 289 experimental studies and grades the evidence for each step linking the printing process to internal structure, surface, contact conditions, wear mechanisms and component life. Four findings stand out. First, the orientation of layers and rasters relative to sliding is associated with a switch between wear controlled by shear of interlayer bonds and wear controlled by crossing of surface ridges; coding orientation as {contact face, layer normal, raster/fibre direction} explains several apparently contradictory results. Second, test conditions dominate absolute wear rates, which for printed neat PEEK span 2.6 decades, with the largest contrast between contact configurations, so effects must be compared within studies. Third, only 3 of 245 full-text studies report all core contact and statistical information; a minimum reporting set is proposed. Fourth, only three printed-versus-conventional comparisons isolate the manufacturing route. Established findings include the failure of hardness as a general wear predictor and friction reduction by oil and grease; lubricant storage in designed porosity remains probable.

Polymers doi: 10.3390/polym18212746

Authors: Bartłomiej Górski Natalia Muczkowska

Soft tissue deficiencies around teeth and dental implants remain a common clinical challenge affecting aesthetics, tissue stability, and long-term maintenance. Polymer-based substitutes reduce donor-site morbidity compared with autogenous connective tissue grafts, but comparative evidence frequently shows lower gains in mucosal thickness and keratinized tissue dimensions. This narrative review examines the biological and material factors that may limit the performance of current soft tissue substitutes and evaluates strategies aimed at overcoming these limitations. Particular attention is given to the mismatch between healing dynamics and passive material behavior, including early burst release of bioactive agents, degradation uncoupled from cellular colonization, delivery kinetics that are not designed to respond to the state of the wound, and limited dose control. Current approaches such as platelet concentrates, recombinant growth factors, affinity-based delivery, covalent immobilization, and cell-seeded matrices can improve selected healing outcomes, but their effects remain strongly dependent on the carrier and have not consistently matched the gains in mucosal thickness and keratinized tissue width obtained with autogenous grafts. Stimuli-responsive and bioresponsive polymer systems offer a potential strategy for making degradation or release depend on the local wound state, although their application in oral soft tissue augmentation remains predominantly preclinical. Future research should focus on polymer–cell and polymer–bioactive agent systems in which degradation, cellular colonization, signal delivery, and mechanical performance are better aligned with tissue healing and long-term maintenance.

Polymers doi: 10.3390/polym18212745

Authors: Nikolaos V. Plachouras Aineias Abedin Stylianos Soranidis Marinos Pitsikalis

The aqueous self-assembly behavior of amphiphilic statistical copolymers, composed of hydrophilic N-vinylpyrrolidone (NVP) and hydrophobic 2-chloroethyl vinyl ether (CEVE), was investigated. Dynamic and static light scattering (DLS and SLS) analyses revealed significant structural variations heavily dependent on the copolymer composition. Specifically, formulations with a high hydrophobic CEVE content exhibited a clear tendency to form highly aggregated systems in aqueous media. These morphological transitions and the resulting supramolecular architectures were visually confirmed via Transmission Electron Microscopy (TEM). The encapsulation capacity of these assemblies was subsequently evaluated using curcumin as a model hydrophobic guest. Despite their inherent statistical sequence, which typically lacks the distinct microphase separation observed in block copolymers, these systems successfully self-assembled and demonstrated high encapsulation efficiency. These findings indicate that such statistical copolymers constitute an effective and structurally simple platform for the entrapment of hydrophobic compounds, underscoring their potential in advanced encapsulation applications.

Polymers doi: 10.3390/polym18212744

Authors: Agnieszka Podolak Justyna Koc-Jurczyk Zuzanna Sylwestrzak Łukasz Jurczyk Waldemar Prokop

Industrial-residue valorisation through polymer-composite manufacturing can reduce reliance on virgin resources, yet the environmental safety of such materials is rarely evaluated beyond conventional physicochemical characterisation. This study provides a novel, integrated assessment of a waste-derived phenol–formaldehyde/glass-fibre composite by combining pH-dependent leaching analysis with a multispecies ecotoxicological test battery. The composite contained post-production glass fibres, paper flakes, and viscose fibres bound with phenol–formaldehyde resin. Under near-neutral extraction conditions, most analysed metals and metalloids showed limited release. In contrast, acidic conditions substantially increased the mobilisation of Ba, Cr, Zn, Cu, and Pb, while the phenol index increased approximately 28-fold, from 0.25 ± 0.06 to 6.9 ± 1.7 mg L−1. Biological responses differed markedly among taxa. Hordeum vulgare and Eisenia andrei showed limited short-term effects, whereas the marine diatom Skeletonema marinoi exhibited pronounced concentration- and time-related inhibition, with no cells detected after three days of exposure to the highest extract loading. The Aliivibrio fischeri assay also revealed concentration-dependent acute toxicity, with the strongest effects observed during the initial exposure period. The pronounced algal response could not be fully explained by the targeted chemical analyses, indicating a possible contribution of unidentified leachable constituents or mixture effects. The novelty of this study lies in demonstrating that technical functionality, waste diversion, and low concentrations of selected regulated contaminants do not alone ensure the environmental safety of waste-derived polymer composites. Integrating stress-condition leaching with sensitive biological endpoints offers a practical framework for safe-by-design formulation, application selection, and end-of-life management. Further studies should address material ageing, repeated leaching, particle release, and non-target identification of bioactive constituents.

Polymers doi: 10.3390/polym18212743

Authors: Huachun Qi Xiaoqi Wang Yuetong Lin Honggang Zhao Jiuyin Pang Yaoxing Sun

Conventional non-biodegradable plastic packaging causes severe environmental pollution, driving the demand for degradable biomass food packaging. Chitosan (CS) is an ideal green film material but suffers weak mechanical, water-resistance and antioxidant properties. Soy protein isolate (SPI) is cheap and abundant; however, its compact molecular structure leads to poor miscibility with pure CS. Herein, ultrasonic-assisted deep eutectic solvent (DES) pretreatment was used to unfold SPI’s protein structure and release active sites for stronger SPI–CS interfacial interactions. Citric acid and transglutaminase (TG) served as dual green crosslinkers, while carvacrol (Car) and gallic acid (GA) were added as natural polyphenol antioxidants. Single-factor and Box–Behnken response surface experiments determined the optimal film-forming parameters: a citric acid mass ratio of 0.84, a TG dosage of 2.60 U∙g−1, and a drying temperature of 65 °C. The optimized DES–SPI–CS film possessed a tensile strength of 18.79 MPa and an elongation at break of 41.39%, with greatly enhanced water resistance and thermal stability. After co-loading Car and GA, the composite film reached 79.33% DPPH radical-scavenging activity. Twelve-day cherry tomato preservation tests confirmed its capacity to slow vitamin C loss and fruit decay. This work provides a sustainable integrated strategy combining DES modification, dual crosslinking and natural antioxidant doping to fabricate multifunctional bio-based packaging, offering theoretical support for biodegradable film substitution of disposable plastics.

Polymers doi: 10.3390/polym18212742

Authors: Mohammad F. Wani Ferdous Ahad Bhat Umida Ziyamukhamedova Mohammad Jebran Khan Lutfillo Bakirov Jasurbek Nafasov Elbek Turgunaliev

In this research study, the effect of laser surface texturing on the tribological performance of a composite of polytetrafluoroethylene with 25 wt.% glass fibre against grey cast iron was studied. Dimples (50 µm diameter) were ablated on grey cast iron with dimple pitches of 100 µm and 150 µm. Friction and wear tests were conducted on a pin-on-disc tribometer under ambient conditions. The specific wear rate of both polytetrafluoroethylene and its composite generally decreased with increasing sliding distance for all grey cast iron surfaces, whether textured or un-textured. The coefficient of friction followed a similar trend for polytetrafluoroethylene but increased for 25 wt.% glass fibre/polytetrafluoroethylene on textured grey cast iron surfaces. Compared to un-textured grey cast iron, polytetrafluoroethylene exhibited a 14.2–16.7% reduction in coefficient of friction and specific wear rate when sliding against grey cast iron with a 150 µm dimple pitch. For 25 wt.% glass fibre/polytetrafluoroethylene, laser surface texturing increased friction but significantly reduced the specific wear rate by 66.6–73.2%. Increasing the dimple pitch from 100 µm to 150 µm further decreased the coefficient of friction and wear. Field Emission Scanning Electron Microscopy micrographs of textured grey cast iron surfaces post sliding against polytetrafluoroethylene revealed polymer debris deposition, which led to the formation of transfer films that contributed to friction and wear reduction. These findings highlight the potential of laser surface texturing in enhancing the tribological performance of polytetrafluoroethylene-based materials, particularly in optimizing wear resistance and friction control through surface texturing.

Polymers doi: 10.3390/polym18212740

Authors: Bekbossyn Kassymbayev Adilkhan Niyazbayev Issa Tailer Yelaman Zhumagaliyev Baydaulet Urmashev Aliya Borsikbayeva Yerzhigit Saparbayev Marat Khazimov

This study presents an experimental and numerical investigation of the sealing performance of welded joints in flexible polyethylene containers subjected to external pressure during vacuum compaction of forage material. The objective was to improve the reliability of welded seams under vacuum gauge pressures of up to 75 kPa. A three-dimensional transient heat-conduction model was developed to investigate the thermal behavior of polyethylene film during heat sealing. The governing heat-conduction equation was solved using ANSYS Fluent based on the finite volume method, employing a pressure-based transient solver and first-order implicit time discretization. Temperature distributions and their temporal evolution, T(t), were determined at selected locations within the film. The strength of welded joints in thin polyethylene films subjected to pressure loading of up to 75 kPa was experimentally evaluated as a function of weld-seam width and clamping force at a selected heat-sealing temperature of 175 °C. High-density polyethylene film (PE-180) with a thickness of 200 μm was used to carry out research specimens measuring 100 × 100 mm. The experimental results were analyzed using a design-of-experiments approach, and a regression equation was developed to describe the dependence of welded-joint strength on seam width and clamping force. The combined numerical and experimental findings provide a basis for selecting appropriate heat-sealing parameters to enhance the reliability of welded seams at the neck of flexible polyethylene containers subjected to vacuum-induced loading.

Polymers doi: 10.3390/polym18212741

Authors: Xin Zheng Susu Jin Shuyao Zhu Tao Lee Zhaohui Jin

Self-assembling peptide hydrogels (SAPHs) have emerged as promising platforms for mucosal drug delivery due to their excellent biocompatibility, programmable sequence design, and diverse triggering strategies. This review systematically discusses the molecular basis, synthesis techniques, and triggering strategies of SAPHs, highlighting how these elements collectively enable in situ gelation and on-demand drug release at mucosal sites. We also review applications across the oral, gastrointestinal, ocular, vaginal, middle ear, and respiratory mucosa, demonstrating the therapeutic potential of SAPHs in infection treatment, tissue repair, and immunomodulation. We further compare SAPHs with other mucosal delivery systems and summarize the clinical status of mucosal delivery products; although several products are in clinical use, no SAPH-based product has been approved for mucosal delivery, and the factors limiting clinical translation are discussed. Despite significant progress, several challenges remain, including balancing mechanical stability with degradation, ensuring batch-to-batch consistency, confirming long-term biosafety, and obtaining regulatory approval. With the integration of artificial intelligence-assisted design and modular programmable platforms, SAPHs hold considerable promise for precision mucosal drug delivery.