Polymers

17 pages, 10712 KB

Open AccessArticle

An Euler Graph-Based Path Planning Method for Additive Manufacturing Thin-Walled Cellular Structures of Continuous Fiber-Reinforced Thermoplastic Composites

by Guocheng Liu, Fei Wang, Qiyong Tu, Ning Hu, Zhen Ouyang, Wenting Wei, Lei Yang and Chunze Yan

Polymers 2025, 17(23), 3236; https://doi.org/10.3390/polym17233236 - 4 Dec 2025

Viewed by 615

Abstract

Thin-walled cellular structures of continuous fiber-reinforced thermoplastic composites (CFRTPCs) have received much attention from both academics and industry due to their superior properties. Additive manufacturing provides an efficient solution for fabricating these thin-walled cellular structures of CFRTPCs. However, the process often requires cutting [...] Read more.

Thin-walled cellular structures of continuous fiber-reinforced thermoplastic composites (CFRTPCs) have received much attention from both academics and industry due to their superior properties. Additive manufacturing provides an efficient solution for fabricating these thin-walled cellular structures of CFRTPCs. However, the process often requires cutting fiber filaments at jumping points during printing. Furthermore, the filament may twist, fold, and break due to sharp turns in the printing path. These issues adversely affect the mechanical properties of the additive manufactured part. In this paper, a Euler graph-based path planning method for additive manufacturing of CFRTPCs is proposed to avoid jumping and sharp turns. Euler graphs are constructed from non-Eulerian graphs using the method of doubled edges. An optimized Hierholzer’s algorithm with pseudo-intersections is proposed to generate printing paths that satisfy the continuity, non-crossing, and avoid most of the sharp turns. The average turning angle was reduced by up to

20.88 %

and the number of turning angles less than or equal to

120 °

increased by up to

26.67 %

using optimized Hierholzer’s algorithm. In addition, the generated paths were verified by house-made robot-assisted additive manufacturing equipment. Full article

(This article belongs to the Special Issue Advanced Fiber-Reinforced Polymer Composites: Design, Manufacturing, Characterization, and Application)

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16 pages, 5350 KB

Open AccessArticle

Mechanism of Interfacial Slippage in the Micro-Triangle and Composite Fiber Membrane Characteristics in Rotary-Force Spinning

by Jianwei Ma, Meng Zhang, Shuo Zhao, Zhiming Zhang, Zhen Chen and Qiaoling Ji

Polymers 2025, 17(23), 3235; https://doi.org/10.3390/polym17233235 - 4 Dec 2025

Viewed by 345

Abstract

Composite fiber membranes fabricated via rotational-force spinning have become widely applied in biomedicine, energy, and environmental fields owing to their excellent properties. Improving their functional performance and fabrication quality has therefore become a key research focus. Rotational-force spinning is a simple and efficient [...] Read more.

Composite fiber membranes fabricated via rotational-force spinning have become widely applied in biomedicine, energy, and environmental fields owing to their excellent properties. Improving their functional performance and fabrication quality has therefore become a key research focus. Rotational-force spinning is a simple and efficient technique in which high-speed motor rotation ejects polymer solutions from a nozzle to form fibers. However, the influence of polymer flow behavior within the nozzle on fiber formation remains insufficiently understood. In this study, the flow characteristics within the micro-triangle and the liquid–liquid slip phenomenon were investigated using a core–shell spinning device. Numerical simulations were conducted to analyze velocity differences between two polymer solutions under varying motor speeds and polyoxyethylene (PEO) concentrations. The results demonstrate that increasing PEO concentration and motor speed decreases slip velocity, thereby stabilizing the flow. Complementary experiments were performed using PEO and hydroxyethyl cellulose (HEC) solutions under controlled conditions. Mechanical testing, scanning electron microscopy (SEM), and thermogravimetric analysis (TG) were employed to assess the mechanical performance, thermal stability, morphology, and fiber diameter distribution of the composite membranes. Overall, the findings highlight the critical role of liquid–liquid slip in fiber formation and provide valuable insights for the controlled fabrication of high-quality composite fibers, offering a foundation for future research. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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21 pages, 5339 KB

Open AccessArticle

Preparation of Alginate/AgNP Nanocomposite Hydrogels Incorporating Olive Leaf Extracts in Natural Deep Eutectic Solvents

by Ioanna Pitterou, Athina Tzavara Roussi, Aikaterini Malliaraki, Elli Martina Kousouli, Andromachi Tzani, Konstantinos Tsiantas, Anthimia Batrinou, Christina Fountzoula, Anastasios Kriebardis, Panagiotis Zoumpoulakis and Anastasia Detsi

Polymers 2025, 17(23), 3234; https://doi.org/10.3390/polym17233234 - 4 Dec 2025

Viewed by 524

Abstract

In the present study, alginate–silver nanoparticle (Alg-AgNP) nanocomposite hydrogels possessing antibacterial activity were synthesized via an innovative route. A task-specific designed Natural Deep Eutectic Solvent (NADES), composed of glucose, lactic acid, and water, was utilized as a green extraction solvent of bioactive compounds [...] Read more.

In the present study, alginate–silver nanoparticle (Alg-AgNP) nanocomposite hydrogels possessing antibacterial activity were synthesized via an innovative route. A task-specific designed Natural Deep Eutectic Solvent (NADES), composed of glucose, lactic acid, and water, was utilized as a green extraction solvent of bioactive compounds from olive leaves (OLs). The NADES–olive leaf extract (NADES-OLE) was used as obtained for the preparation of the Alg-AgNP nanocomposite hydrogel as a multiple-role component. The NADES-OLE acts (a) as a crosslinking agent for the preparation of the alginate hydrogels, (b) as a reducing agent for the in situ synthesis of AgNPs during hydrogel formation, and (c) as a bioactivity enhancement agent due to the presence of compounds obtained from the olive leaves. The Alg-AgNP hydrogel preparation process was optimized through a Box–Behnken experimental design. The resulting nanocomposite hydrogels were characterized for their swelling capacity and water retention in phosphate buffer (pH 5.5), achieving 538% swelling capacity within 180 min and 90% water retention after 250 min. The AgNPs formed within the hydrogels were found to have an average size of 103.2 ± 5.6 nm, with a concentration of 1.2 10⁸ ± 2.2 ∗ 10⁷ particles/mL. Antibacterial testing of the nanocomposite hydrogels against foodborne pathogens, including Gram-negative (Escherichia coli, Salmonella Typhimurium, Yersinia enterocolitica) and Gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus), revealed significant antibacterial activity, particularly against E. coli (64.9%), Y. enterocolitica (60.6%), S. aureus (79.1%), and B. cereus (55.3%), at a concentration of 1 mg/mL. Full article

(This article belongs to the Special Issue Polymer-Based Nanoparticles: Synthesis, Characterization and Applications)

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13 pages, 3264 KB

Open AccessArticle

CFD-Based Evaluation of Stirred Tank Designs for High-Viscosity Copolymer Aramid Dope Mixing

by Dong-Hyun Yeo, Hyun-Sung Yoon, Seong-Hun Yu and Jee-Hyun Sim

Polymers 2025, 17(23), 3233; https://doi.org/10.3390/polym17233233 - 4 Dec 2025

Viewed by 476

Abstract

High-viscosity aramid copolymer solutions are widely used in fiber manufacturing and advanced composite applications, but their elevated viscosity poses significant challenges for mixing and agitation processes. This study employs computational fluid dynamics (CFD) simulations to enhance the mixing performance of such systems. Flow [...] Read more.

High-viscosity aramid copolymer solutions are widely used in fiber manufacturing and advanced composite applications, but their elevated viscosity poses significant challenges for mixing and agitation processes. This study employs computational fluid dynamics (CFD) simulations to enhance the mixing performance of such systems. Flow behavior around the impeller was analyzed within a cylindrical stirred tank while varying the number of baffles (0, 2, 4, and 6) and comparing two different impeller designs (A and B). Simulation results showed that installing a sufficient number of baffles—particularly four—effectively suppressed swirling flows commonly observed in high-viscosity fluids, thereby significantly improving mixing efficiency. Additionally, impeller geometry played a critical role in performance: the axial-flow impeller promoted faster homogenization and broader circulation compared with the radial-flow design. Through this CFD-based analysis, this study elucidates the key mechanisms governing mixing in high-viscosity fluids and provides practical design and operational guidelines for industrial stirred tank systems. These findings complement existing empirical guidelines focused on low-viscosity fluids and contribute to improving the efficiency and reliability of high-viscosity polymer processing. Full article

(This article belongs to the Special Issue High-Performance Polymer Materials and Fiber-Reinforced Composites for Engineering Applications)

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24 pages, 6945 KB

Open AccessArticle

Evaluating Environmental Performance of PLA–Cellulose-Based Biocomposites: A Comprehensive Study on Biodegradability, Compostability, and Ecotoxicity

by Vera L. D. Costa, Pedro E. M. Videira, António de O. Mendes, Tomás Duarte, Bruno F. A. Valente, Paula Pinto, Alexandre Gaspar, Tânia Viana, Paulo T. Fiadeiro, Joana M. R. Curto, Maria Emília Amaral, Ana P. Costa and Joana C. Vieira

Polymers 2025, 17(23), 3232; https://doi.org/10.3390/polym17233232 - 4 Dec 2025

Viewed by 903

Abstract

Increasing concerns about environmental issues have recently intensified the search for sustainable alternatives to conventional plastics that minimize ecological impacts. This study evaluates the biodegradability, compostability, and ecotoxicity of a PLA-based biocomposite containing 30–40% micronized cellulose fibers. The material complied with the European [...] Read more.

Increasing concerns about environmental issues have recently intensified the search for sustainable alternatives to conventional plastics that minimize ecological impacts. This study evaluates the biodegradability, compostability, and ecotoxicity of a PLA-based biocomposite containing 30–40% micronized cellulose fibers. The material complied with the European limits for fluorine and heavy metals. Biodegradability was assessed through a respirometric test under thermophilic conditions, achieving 81% degradation in 155 days. Thermophilic compostability was evaluated by monitoring the disintegration of injected products made from the biocomposite pellets and cut into pieces with thicknesses of 1.0 mm and 2.1 mm, revealing that increased specific surface area prolongs composting time. Ecotoxicity was tested through seed germination and plant growth assays on barley, onion, sunflower, tomato, and wheat using the biocomposite mature compost mixed (25% and 50%) with a TÜV Austria certified soil. Results showed species-dependent effects: sunflower germination was enhanced, while other plants experienced slight growth delays. No severe phytotoxicity was observed, except for barley and wheat. Despite the proven biodegradability and compostability, the biocomposite product’s dimensions influence disintegration and decomposition rates. Furthermore, compost applications may have variable effects on plant development. These findings improved knowledge about sustainable materials performance, raising awareness about more responsible design, consumption, and disposal strategies. Full article

(This article belongs to the Special Issue Advances in Bio-Based Polymers for Sustainable Packaging)

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34 pages, 4501 KB

Open AccessReview

Harnessing Cross-Linked Cysteine Scaffolds for Soft Tissue Engineering Applications

by Lusanda Mtetwa, Thashree Marimuthu, Hillary Mndlovu, Mduduzi N. Sithole, Maya M. Makatini and Yahya E. Choonara

Polymers 2025, 17(23), 3231; https://doi.org/10.3390/polym17233231 - 4 Dec 2025

Viewed by 616

Abstract

Biomaterials are either cross-linked ionically, chemically, or physically, or they can be functionalized with amino acids to overcome inherent biocompatibility and stability limitations. Hydrogels for scaffold fabrication have been effectively utilized to promote tissue integration and cellular processes for soft tissue regeneration. Despite [...] Read more.

Biomaterials are either cross-linked ionically, chemically, or physically, or they can be functionalized with amino acids to overcome inherent biocompatibility and stability limitations. Hydrogels for scaffold fabrication have been effectively utilized to promote tissue integration and cellular processes for soft tissue regeneration. Despite significant progress, poor remodeling limitations persist, hence the need for cross-linkers with dynamic adaptability, native tissue mimicry, and controllable degradation. The aim of this review is to highlight cysteine’s capability and potential to cross-link biomaterials using thiol chemistry while discussing the different cross-linking strategies to aid in the fabrication of robust hydrogel inks and bioinks. Furthermore, cysteine’s limitations and research scarcity in soft tissue scaffolds are highlighted for its chemical significance and potential role. The review examines cysteine’s thiol reactions, including disulfide bonds, thiol–ene, thiol–yne, and Michael additions, and cross-linking ability, with a specialized focus on adipose tissue regeneration. The fabrication methods reviewed include 3D bioprinting, electrospinning, films, and nanostructured scaffolds, with a primary focus on 3D bioprinting of hydrogel scaffolds. Cysteine cross-linking enhances the scaffolds’ stability, printability, biocompatibility, degradability, and biological performance of scaffolds with an 85% increase in Young’s modulus. Cysteine adequately enhances the mechanical properties and degradation rates of adipose tissue scaffolds. This review addresses the underexplored use of cysteine cross-linking in soft tissue scaffolds, beyond its common bone tissue applications. Full article

(This article belongs to the Special Issue Polymer-Based Biomaterials for Tissue Engineering Applications)

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14 pages, 2714 KB

Open AccessArticle

Constructing Highly Ordered Continuous BNNS Networks in COP Film to Achieve Excellent Thermal Conduction and Dielectric Performance

by Jialong Jiang, Yi Zheng, Yuan Ji, Hong Wu and Shaoyun Guo

Polymers 2025, 17(23), 3230; https://doi.org/10.3390/polym17233230 - 4 Dec 2025

Viewed by 420

Abstract

To meet the requirement of thermal management of modern electronic devices, polymer composites with high thermal conductivity (TC) and dielectric performance are nowadays in urgent demand. Herein, a highly ordered continuous network of boron nitride nano-sheet (BNNS) was constructed in cyclic olefin polymer [...] Read more.

To meet the requirement of thermal management of modern electronic devices, polymer composites with high thermal conductivity (TC) and dielectric performance are nowadays in urgent demand. Herein, a highly ordered continuous network of boron nitride nano-sheet (BNNS) was constructed in cyclic olefin polymer (COP) films via the forced flow processing in the rubbery state (FFRS), melt-spinning, fiber-alignment, and hot-pressing procedures. The composites exhibited superior TC, low dielectric permittivity, and low dielectric loss simultaneously. The in-plane TC of the composites reached 3.92 W/(mK) when the content of BNNS was at 27 weight percentage (27 wt%), since the procedures improved the face-to-face contact between the BNNS (which was exfoliated, dispersed, and in-plane oriented during FFRS), enhancing the continuity of the BNNS thermally conductive network. Both the TC and the experimental results indicated the outstanding heat dissipation performance of the composites. Meanwhile, the dielectric permittivity and dielectric loss of the 27 wt% BNNS composites were 2.56 and 0.00085 at 10 GHz, respectively, lower than that of the COP-POE matrix. Moreover, the mechanical properties, water vapor permeability, and coefficient of thermal expansion of the composites were excellent. The composites with such highly ordered continuous networks are very promising in high-performance electronic devices. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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18 pages, 9975 KB

Open AccessArticle

Effects of Environmental Factors on the Mechanical Properties of Palm Leaf Manuscripts: Natural Aging, Temperature, Relative Humidity, and Light Radiation

by Wenjie Zhang, Shan Wang and Hong Guo

Polymers 2025, 17(23), 3229; https://doi.org/10.3390/polym17233229 - 4 Dec 2025

Viewed by 409

Abstract

The mechanical properties of palm leaf manuscripts, a unique organic cultural heritage material, are strongly influenced by environmental conditions that directly determine their physical stability and long-term preservation. This study systematically examined the effects of natural and accelerated aging under different temperature, humidity, [...] Read more.

The mechanical properties of palm leaf manuscripts, a unique organic cultural heritage material, are strongly influenced by environmental conditions that directly determine their physical stability and long-term preservation. This study systematically examined the effects of natural and accelerated aging under different temperature, humidity, and light radiation conditions on the mechanical and chemical properties of palm leaf samples. Flexural strength and flexural modulus were measured to assess mechanical degradation, while FT-IR was employed to evaluate chemical structure changes. The results revealed that temperature had a pronounced effect on mechanical performance. At −20 °C, a temporary increase in flexural strength and modulus was observed due to the structural stabilization caused by frozen moisture, followed by a gradual decline attributed to ice crystal rupture and fiber damage. At 25 °C, degradation progressed steadily, while at 100 °C, the material underwent severe shrinkage and deformation, resulting in significant cracking and a subsequent sharp decline in its mechanical properties. Relative humidity also played a critical role: excessive dryness (10% RH) led to shrinkage and cracking, whereas high humidity (90% RH) caused microbial degradation and hydrolysis, both resulting in sharp declines in strength and stiffness. Samples aged at moderate humidity (50% RH) maintained superior mechanical stability. Light radiation further accelerated deterioration of mechanical properties, with UV exposure inducing the most significant loss due to photochemical reactions that disrupted lignin structures. FT-IR analysis confirmed that the degradation of cellulose and hemicelluloses was a significant cause of mechanical weakening. Overall, extreme environmental conditions accelerated both physical and chemical deterioration. Conversely, moderate and stable environments (around 25 °C, 50% RH, and limited light exposure) were found to be optimal for preserving the mechanical and structural stability of palm leaf manuscripts. These findings provide valuable guidance for the long-term conservation and environmental control of ancient organic manuscripts. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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17 pages, 7322 KB

Open AccessArticle

Development of 3D Printing Filament from Poly(Lactic Acid) and Cassava Pulp Composite with Epoxy Compatibilizer

by Thidarat Kanthiya, Pattraporn Changsuwan, Krittameth Kiattipornpithak, Pornchai Rachtanapun, Sarinthip Thanakkasaranee, Pensak Jantrawut, Nuttapol Tanadchangsaeng, Patnarin Worajittiphon, Thorsak Kittikorn and Kittisak Jantanasakulwong

Polymers 2025, 17(23), 3228; https://doi.org/10.3390/polym17233228 - 4 Dec 2025

Viewed by 440

Abstract

A 3D printing filament was fabricated from poly(lactic acid) (PLA), cassava pulp (CP), and epoxy using a twin-screw extruder. Several bio-composites were synthesized by varying the amount of epoxy (0.5, 1.0, 3.0, 5.0, and 10.0 wt.%). The size of the CP fibers significantly [...] Read more.

A 3D printing filament was fabricated from poly(lactic acid) (PLA), cassava pulp (CP), and epoxy using a twin-screw extruder. Several bio-composites were synthesized by varying the amount of epoxy (0.5, 1.0, 3.0, 5.0, and 10.0 wt.%). The size of the CP fibers significantly affected the surface quality, filament diameter, and mechanical properties of the final product. The smallest fiber size (45 µm) provided a smooth surface and consistent diameter. Incorporating 1 wt.% of epoxy into PLA/CP enhanced the tensile strength (56.6 MPa), elongation at break (6.2%), and hydrophobicity of the composite. The composite mechanical properties deteriorated at epoxy contents above 1 wt.% due to the amplified plasticizer effect of excessive epoxy. The optimized PLA/CP/epoxy formulation was used to generate the 3D filament. The resultant filament displayed a tensile strength of 64.6 MPa and elongation at break of 9.8%, attributed to the fine morphology achieved via thorough mixing provided by the twin-screw extruder. Epoxide-mediated crosslinking between PLA and CP enabled the development of a novel 3D printing filament with excellent mechanical properties. This research illustrates how agricultural residues can be upcycled into high-performance biomaterials with innovation in sustainable manufacturing, inclusive economic growth, reducing reliance on petroleum-based plastics and thus providing benefits regarding human health, climate change mitigation, plastic in the ocean, and environmental impacts. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)

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51 pages, 4171 KB

Open AccessReview

Brick by Brick the Wall Is Being Built: Particle-Based Scaffolds for Regenerative Medicine

by Viktor Korzhikov-Vlakh, Lei Wang, Sofia Morozova, Ekaterina Sinitsyna, Tatiana Tennikova and Evgenia Korzhikova-Vlakh

Polymers 2025, 17(23), 3227; https://doi.org/10.3390/polym17233227 - 4 Dec 2025

Viewed by 655

Abstract

Tissue engineering offers a promising solution by developing scaffolds that mimic the extracellular matrix and guide cellular growth and differentiation. Recent evidence suggests that scaffolds must provide not only biocompatibility and appropriate mechanical properties, but also the structural complexity and heterogeneity characteristic of [...] Read more.

Tissue engineering offers a promising solution by developing scaffolds that mimic the extracellular matrix and guide cellular growth and differentiation. Recent evidence suggests that scaffolds must provide not only biocompatibility and appropriate mechanical properties, but also the structural complexity and heterogeneity characteristic of natural tissues. Particle-based scaffolds represent an emerging paradigm in regenerative medicine, wherein micro- and nanoparticles serve as primary building blocks rather than minor additives. This approach offers exceptional control over scaffold properties through precise selection and combination of particles with varying composition, size, rigidity, and surface characteristics. The presented review examines the fundamental principles, fabrication methods, and properties of particle-based scaffolds. It discusses how interparticle connectivity is achieved through techniques such as selective laser sintering, colloidal gel formation, and chemical cross-linking, while scaffold architecture is controlled via molding, templating, cryogelation, electrospinning, and 3D printing. The resulting materials exhibit tunable mechanical properties ranging from soft injectable gels to rigid load-bearing structures, with highly interconnected porosity that is essential for cell infiltration and vascularization. Importantly, particle-based scaffolds enable sophisticated pharmacological functionality through controlled delivery of growth factors, drugs, and bioactive molecules, while their modular nature facilitates the creation of spatial gradients mimicking native tissue complexity. Overall, the versatility of particle-based approaches positions them as prospective tools for tissue engineering applications spanning bone, cartilage, and soft tissue regeneration, offering solutions that integrate structural support with biological instruction and therapeutic delivery on a single platform. Full article

(This article belongs to the Special Issue Polymer Scaffolds for Tissue Engineering, 3rd Edition)

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20 pages, 5941 KB

Open AccessArticle

Polymer Mediated Control and Migration Effects in Spin-Crossover-Polymer Hybrids Towards Tunable Thermal Sensing Applications

by Georgios N. Mathioudakis, Georgios Kaldiris, Solveig Felton, Grace Genevieve Morgan, George A. Voyiatzis and Zoi G. Lada

Polymers 2025, 17(23), 3226; https://doi.org/10.3390/polym17233226 - 4 Dec 2025

Viewed by 483

Abstract

Tailoring the spin crossover (SCO) effect in molecular materials remains a fundamental challenge, driven by the need to control critical parameters, such as the spin transition temperature (T₁/₂), hysteresis width, cooperativity, and switching kinetics for applications in sensing, memory, [...] Read more.

Tailoring the spin crossover (SCO) effect in molecular materials remains a fundamental challenge, driven by the need to control critical parameters, such as the spin transition temperature (T₁/₂), hysteresis width, cooperativity, and switching kinetics for applications in sensing, memory, and actuation devices. SCO behavior is highly sensitive to small changes in the structure or crystal structure of the surrounding environment. In this context, achieving predictable and reproducible control remains elusive. Embedding SCO complexes into polymer matrices offers a more versatile and processable approach, but understanding how matrix–guest interactions affect spin-state behavior is still limited. In this study, we investigate a polymer-mediated strategy to tune SCO properties by incorporating the well-characterized Fe(II) complex [Fe(1,10-phenanthroline)₂(NCS)₂] into three polymers with distinct structural features: polylactic acid (PLA), polystyrene (PS), and polysulfone (PSF). In terms of potential electrostatic interaction between the complex and the polymeric matrixes, the polymers offer distinct features. Either there does not seem to be any specific interaction (PLA case) or, rather, there is π-π stacking between the aromatic rings of the SCO complex, and the corresponding ones present either in the backbone or in the side chain of the polymer (PSF and PS, respectively). The latter can potentially influence spin-state energetics and dynamics. Importantly, we also reveal and quantify the migration behavior of SCO particles within different polymer matrices, an aspect that has not been previously examined in SCO–polymer systems. Using magnetic susceptibility, spectroscopic, diffraction, and migration studies, we show that the polymer environment, PLA as well, actively modulates the SCO response. PSF yields lower T₁/₂, slower switching kinetics, and enhanced retention of the complex, indicative of strong matrix confinement and interaction. In contrast, PLA and PS composites exhibit sharper transitions and higher migration, suggesting weaker interactions and greater mobility. In addition, the semi-crystalline nature of PLA seems to induce the extension of the hysteresis width. These results highlight both the challenge and the opportunity in SCO polymer composites to tune SCO behavior, offering a scalable route toward functional hybrid materials for thermal sensing and responsive devices. Full article

(This article belongs to the Special Issue Polymers in Inorganic Chemistry: Synthesis and Applications)

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24 pages, 3986 KB

Open AccessArticle

From Cellulose to Functional Electrode SCNF:rGO Hybrid Films for Electrochemical Applications

by Josefa Silva, José Raúl Sosa-Acosta, Galo Ramírez, Katherina Fernández and Rodrigo del Rio

Polymers 2025, 17(23), 3225; https://doi.org/10.3390/polym17233225 - 4 Dec 2025

Viewed by 479

Abstract

Sulfated nanocellulose (SCNF) and reduced graphene oxide (rGO) films were fabricated through environmentally friendly methods to develop an effective platform for electrochemical applications. The hybrid materials were extensively characterized by FTIR, XRD, Raman spectroscopy, TGA, SEM, cyclic voltammetry (CV), and electrochemical impedance spectroscopy [...] Read more.

Sulfated nanocellulose (SCNF) and reduced graphene oxide (rGO) films were fabricated through environmentally friendly methods to develop an effective platform for electrochemical applications. The hybrid materials were extensively characterized by FTIR, XRD, Raman spectroscopy, TGA, SEM, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results showed that incorporating rGO into the SCNF matrix significantly improved the electrical conductivity and structural robustness of the films. FTIR confirmed interactions between sulfate groups on cellulose and residual oxygen-containing groups on rGO, while XRD and Raman analyses indicated reduced crystallinity and increased structural disorder, supporting the successful integration of both phases. XPS further demonstrated that SCNF and rGO form chemical bonds rather than simply mixing, with both components remaining active at the surface—evidence of strong interfacial interactions that contribute to enhanced stability and efficient charge transfer. The 1:5 (rGO:SCNF) composition showed the best electrochemical performance, exhibiting minimal charge-transfer resistance and improved hydrazine oxidation, as reflected by a shift of the anodic peak potential toward lower values. Additionally, functionalization with cobalt porphyrin significantly boosted catalytic activity. Overall, the SCNF:rGO films offer a sustainable and scalable platform for electrochemical sensing and energy-conversion applications, demonstrating excellent adaptability and functional performance. Full article

(This article belongs to the Topic Application of Graphene-Based Materials, 2nd Edition)

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13 pages, 1621 KB

Open AccessArticle

Starch–Citric Acid Adhesive: Preparation and Performance Study Catalyzed by p-Toluenesulfonic Acid

by Jiankun Liang, De Li, Zhongyou Luo, Yuqi Yang, Tong Meng, Chuchu Chen, Huali Li, Ningyuan Zuo, Qiuli Li, Hui Yang and Zhigang Wu

Polymers 2025, 17(23), 3224; https://doi.org/10.3390/polym17233224 - 3 Dec 2025

Viewed by 656

Abstract

This study investigates the application effects of p-toluenesulfonic acid (p-TsOH) as an efficient catalyst in the esterification reaction of starch–citric acid adhesives, aiming to successfully prepare plywood with good water resistance through lower hot-pressing temperatures. By precisely controlling the addition ratio of pTSA [...] Read more.

This study investigates the application effects of p-toluenesulfonic acid (p-TsOH) as an efficient catalyst in the esterification reaction of starch–citric acid adhesives, aiming to successfully prepare plywood with good water resistance through lower hot-pressing temperatures. By precisely controlling the addition ratio of pTSA (0–10%), the multifaceted impacts on the adhesive’s curing behavior, bonding strength, water resistance, thermal stability, and microstructure were analyzed. The results demonstrate that pTSA substantially catalyzes the esterification crosslinking reaction between starch and citric acid. Differential scanning calorimetry (DSC) analysis reveals a significant reduction in the reaction peak temperature from 197.7 °C to 154.3 °C, which effectively lowers the hot-pressing temperature and provides more energy-efficient processing conditions for plywood production. When pTSA addition is within the range of 6–8%, the adhesive exhibits superior bonding performance and water resistance. Moreover, thermal stability is significantly enhanced and the microstructure becomes denser, collectively improving the overall performance of the plywood. This study not only provides a solid theoretical basis for the development of high-performance, environmentally friendly, starch-based wood adhesives but also offers strong technical support for the practical application of related technologies expected to promote the green and sustainable development of the wood adhesive industry. Full article

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14 pages, 2793 KB

Open AccessArticle

Influence of Epichlorohydrin Concentration on the Physicochemical and Rheological Performance of Lignin/PVA Hydrogels

by Nazish Jabeen, Paula G. Garnero, Rafael Muñoz-Espí, Clara M. Gómez and Mario Culebras

Polymers 2025, 17(23), 3223; https://doi.org/10.3390/polym17233223 - 3 Dec 2025

Viewed by 473

Abstract

This study investigates the influence of epichlorohydrin (EPCH) concentration on the rheological, mechanical, and swelling properties of lignin/PVA hydrogels. Hydrogels were prepared with EPCH concentrations ranging from 2.5% to 7.5%, and their viscoelastic properties were characterized through oscillatory strain and frequency sweep rheology. [...] Read more.

This study investigates the influence of epichlorohydrin (EPCH) concentration on the rheological, mechanical, and swelling properties of lignin/PVA hydrogels. Hydrogels were prepared with EPCH concentrations ranging from 2.5% to 7.5%, and their viscoelastic properties were characterized through oscillatory strain and frequency sweep rheology. Increasing the EPCH concentration led to a substantial rise in mechanical stiffness, with the compressive modulus increasing from 21 kPa (2.5%) to 275 kPa (7.5%), accompanied by a marked reduction in swelling capacity from 460% to 190%. This behavior is attributed to the formation of a denser and more interconnected network structure with increasing cross-linking density. Furthermore, a strong correlation was observed between EPCH concentration and gelation kinetics, with higher concentrations generally leading to faster gelation times. In all formulations, gel time consistently decreased as the temperature increased from 10 to 50 °C. The optimal EPCH concentration for achieving a balance between mechanical properties and processability was determined to be 3.5%. At this concentration, the hydrogels exhibited a favorable combination of mechanical strength, shape recovery, and processability, while maintaining desirable swelling behavior. These findings provide valuable insights into the critical role of cross-linking density in determining the physicochemical properties of lignin/PVA hydrogels, paving the way for the development of these bio-based materials with tailored properties for diverse applications. Full article

(This article belongs to the Special Issue Lignin-Based Functional Materials)

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44 pages, 2869 KB

Open AccessReview

Abiotic Degradation Technologies to Promote Bio-Valorization of Bioplastics

by Karen Gutiérrez-Silva, Natalia Kolcz, Maria C. Arango, Amparo Cháfer, Oscar Gil-Castell and Jose D. Badia-Valiente

Polymers 2025, 17(23), 3222; https://doi.org/10.3390/polym17233222 - 3 Dec 2025

Viewed by 609

Abstract

Biodegradable bioplastics have emerged as a promising sustainable alternative to minimize the environmental impact of traditional plastics. Nevertheless, many of them degrade slowly under natural or industrial conditions, raising concerns about their practical biodegradability. This fact is related to the high-order structure of [...] Read more.

Biodegradable bioplastics have emerged as a promising sustainable alternative to minimize the environmental impact of traditional plastics. Nevertheless, many of them degrade slowly under natural or industrial conditions, raising concerns about their practical biodegradability. This fact is related to the high-order structure of the polymer backbones, i.e., high molar mass and high crystallinity. Research efforts are being devoted to the development of technologies capable of reducing the length of polymer segments by accelerated chain scission, which could help improve biodegradation rates upon disposal of bioplastic products. The objective of this review is to examine the current state of the art of abiotic degradation techniques, physically driven by temperature, mechanical stress, UV/gamma/microwave irradiation, or plasma or dielectric barrier discharge, and chemically induced by ozone, water, or acidic/basic solutions, with the aim of enhancing the subsequent biodegradation of bioplastics in controlled valorization scenarios such as composting and anaerobic digestors. Particular attention is given to pretreatment degradation technologies that modify surface properties to enhance microbial adhesion and enzymatic activity. Technologies such as ozonation and plasma-driven treatments increase surface hydrophilicity and introduce functional groups with oxygen bonds, facilitating subsequent microbial colonization and biodegradation. Irradiation-based techniques directly alter the chemical bonds at the polymer surface, promoting the formation of free radicals, chain scission, and crosslinking, thereby modifying the polymer structure. Pretreatments involving immersion in aqueous solutions may induce solution sorption and diffusion, together with hydrolytic chain breakage in bulk, with a relevant contribution to the ulterior biodegradation performance. By promoting abiotic degradation and increasing the accessibility of biopolymers to microbial systems, these pretreatment strategies can offer effective tools to enhance biodegradation and, therefore, the end-of-life management of bioplastics, supporting the transition toward sustainable cradle-to-cradle pathways within a biocircular economy. Full article

(This article belongs to the Special Issue Technological Routes for the Valorisation of Plastic Waste: Degradation Mechanisms and Sustainable Approaches)

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16 pages, 2866 KB

Open AccessArticle

Bifunctionalized Polyethyleneimine-Based Sponge for Adsorption of Ibuprofen from Aqueous Solution

by Xiaoyi Gou, Zia Ahmad, Zaijin You and Zhou Ren

Polymers 2025, 17(23), 3221; https://doi.org/10.3390/polym17233221 - 3 Dec 2025

Viewed by 471

Abstract

A quaternized and phenyl-functionalized hyperbranched PEI-based sponge (S_HPEI-QP) was successfully prepared, and its adsorption performance was investigated to evaluate its potential for removing the anionic non-steroidal anti-inflammatory drug (ibuprofen (IBU)). We reported that the synthesis of polyethyleneimine-based sponges was achieved through [...] Read more.

A quaternized and phenyl-functionalized hyperbranched PEI-based sponge (S_HPEI-QP) was successfully prepared, and its adsorption performance was investigated to evaluate its potential for removing the anionic non-steroidal anti-inflammatory drug (ibuprofen (IBU)). We reported that the synthesis of polyethyleneimine-based sponges was achieved through cryo-polymerization using 1,4-butanediol diglycidyl ether (BDDE) as the crosslinking agent. Subsequent functionalization with resorcinol diglycidyl ether (RDGE) and trimethylamine introduced quaternary ammonium cations, imparting strong basicity and hydrophilicity, as well as phenyl groups, conferring hydrophobic characteristics, respectively. The aforementioned sponge material, S_HPE-QPI, primarily facilitates the efficient adsorption of IBU in aqueous solutions through the anion exchange properties of quaternary ammonium groups and the π-π interactions associated with oxygen-activated benzene rings. Various characterizations, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and specific surface area determination method (BET), confirmed the successful synthesis of the bifunctionalized S_HPEI-QP adsorbent. This adsorbent features a porous structure (specific surface area of 77.2 m² g⁻¹ and pore size distribution of 25–100 nm) and an isoelectric point (pH_pzc) of 9.38. The adsorption kinetics of the adsorbent for IBU were extremely rapid and conformed to a pseudo-second-order kinetic model, and the adsorption isotherm aligned with the Langmuir isotherm model. Noteworthily, S_HPEI-QP demonstrated an exceptionally high adsorption capacity for IBU, achieving a maximum uptake of 905.73 mg g⁻¹ at pH 7.0, which surpassed that of most of the previous reported adsorbents. Moreover, the sponge material can be chemically regenerated. After eight cycles of use, the adsorption efficiency decreased by only 4%. These findings suggest that the synthesized dendritic anion exchange adsorbent represents a promising candidate for the removal of IBU from contaminated water sources. Full article

(This article belongs to the Section Polymer Applications)

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21 pages, 3560 KB

Open AccessArticle

Novel Superelastic Polyesters Based on 2,5-Furandicarboxylic Acid for Potential Use in Ophthalmic Surgery

by Arianna Palumbo, Gloria Astolfi, Giulia Guidotti, Michelina Soccio, Elisa Boanini, Piera Versura and Nadia Lotti

Polymers 2025, 17(23), 3220; https://doi.org/10.3390/polym17233220 - 3 Dec 2025

Viewed by 493

Abstract

The rapid development of ophthalmic surgery in recent years has made big steps forward, making interventions such as penetrating and lamellar keratoplasty or trabeculectomy widely practiced. However, the use of non-absorbable sutures in these procedures poses significant challenges. Indeed, unequal tension between the [...] Read more.

The rapid development of ophthalmic surgery in recent years has made big steps forward, making interventions such as penetrating and lamellar keratoplasty or trabeculectomy widely practiced. However, the use of non-absorbable sutures in these procedures poses significant challenges. Indeed, unequal tension between the various stitches can lead to deformations of the cornea or lens and consequently to problems such as post-operative astigmatism or anisometropia. To overcome these problems, sutures with improved closure via a highly stretchable behaviour together with an excellent elastic return are a credible solution. Accordingly, to widen the plethora of superelastic polymeric materials, in the present study a novel solution deriving from two furan-based polyesters, poly(pentamethylene furanoate), PPeF, and poly(hexamethylene furanoate), PHF, was successfully obtained. Of note, these homopolymers are also entirely derived from sustainable sources. The two homopolymers were physically and chemically mixed to obtain copolymers with different block lengths, which were characterised from molecular, thermal, mechanical, and surface wettability points of view, showing interesting properties which were easily modulated as a function of block length. Lastly, all the materials showed good stability over time and cell viability and, for some of them, a great mechanical recovery upon deformation was also observed. Full article

(This article belongs to the Special Issue Stimuli-Responsive Polymers: Advances and Prospects)

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27 pages, 8117 KB

Open AccessArticle

Development and Characterization of Laminated Composites from Açaí Residues and Castor Oil-Based Polyurethane Matrix

by Jorge Bastos Gaby Filho, Maurício Maia Ribeiro, Douglas Santos Silva, Raí Felipe Pereira Junio, José de Ribamar Mouta Araújo, Roberto Paulo Barbosa Ramos, Sergio Neves Monteiro and Jean da Silva Rodrigues

Polymers 2025, 17(23), 3219; https://doi.org/10.3390/polym17233219 - 3 Dec 2025

Viewed by 366

Abstract

This work presents the development and characterization of laminated composite panels produced from açaí residues and fibers, incorporated into a castor oil-based vegetable polyurethane matrix. The study aimed to evaluate the potential of these Amazonian agro-industrial residues as lignocellulosic reinforcement in sustainable materials. [...] Read more.

This work presents the development and characterization of laminated composite panels produced from açaí residues and fibers, incorporated into a castor oil-based vegetable polyurethane matrix. The study aimed to evaluate the potential of these Amazonian agro-industrial residues as lignocellulosic reinforcement in sustainable materials. The manufacturing process was carried out by manual lamination and cold pressing, following the recommendations of ABNT NBR 14810-2:2018. The physical (moisture, density, and swelling) and mechanical (perpendicular tensile and static flexural) properties of the resulting panels were analyzed. The results revealed an average moisture content of 6.23% and a 24 h swelling of 2.76%, which are values within and well below the regulatory limits, respectively. The perpendicular tensile strength (0.49 N/mm²) exceeded the minimum required value, indicating good interfacial adhesion and internal cohesion. However, the flexural strength and modulus of elasticity (2.4 N/mm² and 1323 N/mm²) were below the standards due to the absence of oriented fibers and density heterogeneity. It is concluded that the composite has high potential for indoor applications with low structural stress, standing out for its lightness, dimensional stability and environmental viability in the use of açaí residues. Full article

(This article belongs to the Special Issue Advances in Composite Materials: Polymers and Fibers Inclusion)

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36 pages, 18724 KB

Open AccessArticle

Statistical Optimization of Graphene Nanoplatelet-Reinforced Epoxy Nanocomposites via Box–Behnken Design for Superior Flexural and Dynamic Mechanical Performance

by Júlia Mendes, Camila Prudente Magalhães, Letícia Vitorazi, Noemi Raquel Checca Huaman, Sergio Neves Monteiro, Teresa Gómez-del Río and Ulisses Oliveira Costa

Polymers 2025, 17(23), 3218; https://doi.org/10.3390/polym17233218 - 3 Dec 2025

Viewed by 522

Abstract

Graphene nanoplatelets (GNPs) are efficient nanofillers for improving the mechanical and thermal properties of epoxy resins due to their high stiffness, aspect ratio, and interfacial reinforcement ability. This study employs a three-factor, three-level Box–Behnken Design (BBD) to investigate the combined effect of GNP [...] Read more.

Graphene nanoplatelets (GNPs) are efficient nanofillers for improving the mechanical and thermal properties of epoxy resins due to their high stiffness, aspect ratio, and interfacial reinforcement ability. This study employs a three-factor, three-level Box–Behnken Design (BBD) to investigate the combined effect of GNP content (0.5–3.5 wt.%), hardener concentration (9–17 phr), and post-curing temperature (30–120 °C) on DGEBA/TETA epoxy nanocomposites. Mechanical, thermal, dynamic mechanical, and morphological characterizations (flexural testing, DMA, TGA, DSC, FTIR, SEM, TEM, and AFM) established structure–property correlations. The optimized formulation (2.0 wt.% GNP, 9 phr hardener, and 120 °C post-curing) exhibited superior reinforcement, with flexural strength of 322.0 ± 12.8 MPa, flexural modulus of 9.7 ± 0.5 GPa, and strain at break of 4.4 ± 0.2%, corresponding to increases of 197%, 155%, and 91% compared with neat epoxy. DMA confirmed a rise in storage modulus from 2.9 to 7.5 GPa and a Tg of 143 °C, while TGA showed a 15 °C improvement in thermal stability. Statistical analysis identified post-curing temperature as the dominant factor governing Tg, stiffness, and thermal stability, with synergistic contributions from GNP content and hardener concentration to the overall network performance. These results surpass those of GO- and CNT-based systems, demonstrating the superior efficiency of GNPs under optimized conditions. The proposed approach provides a robust pathway for developing epoxy nanocomposites with low filler content and enhanced multifunctional performance. Full article

(This article belongs to the Special Issue Polymer Composites: Structure, Properties and Processing, 2nd Edition)

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5 pages, 156 KB

Open AccessEditorial

Selected Papers in 2023–2024 in the “Polymer Membranes and Films” Section

by Yuekun Lai

Polymers 2025, 17(23), 3217; https://doi.org/10.3390/polym17233217 - 3 Dec 2025

Viewed by 606

Abstract

In recent years, research within the “Polymer Membranes and Films” Section has increasingly reflected a convergence of molecular engineering, interfacial design, and processing innovation aimed at achieving both performance enhancement and environmental responsibility [...] Full article

(This article belongs to the Section Polymer Membranes and Films)

30 pages, 6939 KB

Open AccessArticle

Geopolymerization of Kaolin Clay with Hemp Fibers for Sustainable Soil Stabilization

by Bilge Aksu Alcan, Halil Oğuzhan Kara and Mehmet Uğur Yılmazoğlu

Polymers 2025, 17(23), 3216; https://doi.org/10.3390/polym17233216 - 2 Dec 2025

Viewed by 493

Abstract

In this study, the aim was to improve the mechanical and durability properties of kaolin clay (KC)-based soil by stabilizing it with geopolymer and natural fiber. In the production of the geopolymer, rice husk ash (RHA) was used as a binder, sodium metasilicate [...] Read more.

In this study, the aim was to improve the mechanical and durability properties of kaolin clay (KC)-based soil by stabilizing it with geopolymer and natural fiber. In the production of the geopolymer, rice husk ash (RHA) was used as a binder, sodium metasilicate (SMS) as an activator, and another hemp fiber (HF)was used for soil stabilization. Within the scope of the presented study, RHA and SMS were used at three different rates (5%, 7.5%, and 10%), while HF was used in six different volumes (0.5%, 1%, 1.5%, 2%, 2.5%, and 3%) and two different lengths (6 and 12 mm). The study also examined how much water was in the combinations, which was measured at the optimum level and at −5, +5, and +10 compared to the optimum level. The unconfined compressive strength (UCS) was used to check the mechanical qualities of the test specimens and 5- and 10-cycle freeze–thaw (F-T) tests to check the durability properties. The test results indicated that the mixed formulation with 5% RHA, 10% SMS, 2.5% HF, and the optimum water content resulted in the best results for both the UCS and F-T tests. The SEM investigation for this mix found that the microstructural properties for the specimen were directly related to the dense gel phases and the strong fiber–matrix bonding. According to the carbon emissions (CO₂-e) and carbon index (CI) analysis from the mix component analyses, it was found that the HF-strengthened geopolymer is a sustainable solution for soil stabilization. The optimum mixture achieved a UCS of 1202 kPa (4.5 times higher than untreated soil), while the strength losses after 10 freeze–thaw cycles were reduced to below 10% in optimized compositions. The carbon index (CI) decreased by up to 65%, demonstrating the strong sustainability benefits of the proposed system. The novelty of this study lies in the combined use of hemp fiber (HF) and rice husk ash (RHA)–sodium metasilicate (SMS)-based geopolymer for kaolin clay stabilization, which has not been comprehensively investigated in previous research. Unlike traditional studies focusing on either geopolymer or natural fiber reinforcement alone, this work simultaneously evaluates the mechanical performance, freeze–thaw durability, microstructural evolution, and carbon footprint to develop a fully sustainable soil improvement framework. Full article

(This article belongs to the Special Issue Recent Advances and Innovative Applications of Polymer-Enhanced Composites in Construction)

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19 pages, 3934 KB

Open AccessArticle

Evaluation of the Effectiveness and Safety of New Wound Coatings Based on Cod Collagen for Fast Healing of Burn Surfaces

by Anna Soloveva, Lyudmila Semenycheva, Victoria Rumyantseva, Yulia Kuznetsova, Veronika Prodaevich, Natalia Valetova, Petr Peretyagin, Natalia Didenko, Ksenia Belyaeva, Diana Fukina, Maria Vedunova and Evgeny Suleimanov

Polymers 2025, 17(23), 3215; https://doi.org/10.3390/polym17233215 - 2 Dec 2025

Viewed by 393

Abstract

Wound coatings in the form of sponge plates were obtained based on hydrogels of cod collagen (CC) copolymers. The synthesis of CC copolymers with pectin was carried out in the presence of a triethylbor–hexamethylenediamine (TEB-HMDA) complex, which forms free radicals under reaction conditions, [...] Read more.

Wound coatings in the form of sponge plates were obtained based on hydrogels of cod collagen (CC) copolymers. The synthesis of CC copolymers with pectin was carried out in the presence of a triethylbor–hexamethylenediamine (TEB-HMDA) complex, which forms free radicals under reaction conditions, and with polyethylene glycol (PEG) during photocatalysis in the presence of RbTe_1.5W_0.5O₆ oxide under visible-light irradiation with a LED lamp. Evaluation of their effectiveness and safety for rapid healing of wounds and burn surfaces has been conducted on small animals (rats). It has shown significantly higher efficiency in comparison with commercial collagen sponges based on bovine collagen. Coatings based on cod collagen contributed to the normalization of microcirculation levels according to the results of laser Doppler flowmetry and a high rate of reduction in the area of the scalped burn wound according to planimetry. The morphological studies indicate complete epithelialization with the formation of scar tissue in all studied groups of animals. The dynamics of microcirculation parameters indicate the repair of thermal burns during local treatment with wound-healing coatings against the background of normalization of the functioning of the microcirculatory system. It is advisable to use new collagen-based polymer sponge plates to increase the effectiveness of wound treatment of various origins, shorten recovery time, and optimize the course of typical physiological reactions during the wound process in order to accelerate tissue regeneration, as well as reduce mortality. Full article

(This article belongs to the Special Issue Research on Functional Polymer-Based Coatings)

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11 pages, 2479 KB

Open AccessArticle

Low Power Consumption Silica Thermo-Optic Switch Based on Polymer Cladding

by Tianyu Zhong, Jiale Qin, Wenqian Liu, Yuqi Xie, Chahao An, Yinxiang Qin and Yunji Yi

Polymers 2025, 17(23), 3214; https://doi.org/10.3390/polym17233214 - 2 Dec 2025

Viewed by 360

Abstract

Silica-based splitters, couplers, and arrayed waveguide gratings are key components in optical communication. However, the high tuning power consumption of silica chips limits their development and application in fields such as Reconfigurable Optical Add/Drop Multiplexers and Mode Division Multiplexing. In this work, we [...] Read more.

Silica-based splitters, couplers, and arrayed waveguide gratings are key components in optical communication. However, the high tuning power consumption of silica chips limits their development and application in fields such as Reconfigurable Optical Add/Drop Multiplexers and Mode Division Multiplexing. In this work, we demonstrate a silica thermo-optic switch based on polymer cladding within a Mach–Zehnder Interferometer framework, in which a UV-curable polymer is employed as the upper cladding to enhance thermal efficiency. The device exhibits a power consumption of 48 mW, rise and fall response times were 215 µs and 271 µs, compared to all-silicon switches, the power consumption is reduced by 75%, and the switching speed is improved by nearly a factor of two, while maintaining a comparable insertion loss. Experimental results demonstrate an insertion loss of 8.53 dB and an extinction ratio of 10.12 dB. Full article

(This article belongs to the Section Polymer Applications)

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26 pages, 6964 KB

Open AccessArticle

Polypropylene Dissolution Kinetics: Effects of Solvent, Temperature, and Particle Size

by Paschalis Alexandridis, Ali Ghasemi and Marina Tsianou

Polymers 2025, 17(23), 3213; https://doi.org/10.3390/polym17233213 - 2 Dec 2025

Viewed by 753

Abstract

Polypropylene (PP) is widely used and currently very little recycled. A promising method for recycling the PP present in plastic waste involves its selective dissolution and subsequent separation from undissolved compounds. We address here the fundamentals of PP dissolution. Specifically, we present a [...] Read more.

Polypropylene (PP) is widely used and currently very little recycled. A promising method for recycling the PP present in plastic waste involves its selective dissolution and subsequent separation from undissolved compounds. We address here the fundamentals of PP dissolution. Specifically, we present a model that describes the different phenomena involved in the dissolution of semicrystalline PP and validate the model with the experimental results on the decrystallization and dissolution kinetics of PP pellets. The model provides detailed time-resolved and position-resolved information on composition (i.e., crystalline PP, amorphous PP, and solvent) and solvent diffusivity (which depends on composition) across the dissolving polymer particle, in different solvents and temperatures. Such information is unavailable experimentally or difficult to obtain. The key fitted parameters that capture decrystallization and polymer chain disentanglement decrease with increasing temperature following an Arrhenius relationship, with activation energies higher than that for crystallization and comparable to that for melt viscosity. Both decrystallization and dissolution times increase with particle size. For smaller particles, decrystallization and dissolution occur nearly simultaneously, while for larger particles, their interior remains solvent-poor and crystalline for longer times. This work offers insights into the interplay of decrystallization and polymer chain disentanglement during the time-course of PP dissolution. Further, this work facilitates the design and optimization of a dissolution–precipitation recycling process that can unlock value from the million tons of PP annually that is currently being landfilled or incinerated following its use. Full article

(This article belongs to the Section Circular and Green Sustainable Polymer Science)

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18 pages, 4352 KB

Open AccessArticle

Immobilization of Trypsin and Lysozyme in Halloysite Nanotubes for Producing Chitosan Coatings with Antibacterial Properties

by Yuliya Cherednichenko, Ilnur Ishmukhametov, Svetlana Batasheva, Gölnur Fakhrullina and Rawil Fakhrullin

Polymers 2025, 17(23), 3212; https://doi.org/10.3390/polym17233212 - 2 Dec 2025

Viewed by 467

Abstract

A simple method for producing a nanocomposite based on halloysite nanotubes modified with carboxymethylcellulose and trypsin and lysozyme enzymes was developed. Fourier transform infrared spectroscopy confirmed the presence of enzymes in the samples. Chitosan-based coatings were subsequently produced from the nanocomposites. Atomic force [...] Read more.

A simple method for producing a nanocomposite based on halloysite nanotubes modified with carboxymethylcellulose and trypsin and lysozyme enzymes was developed. Fourier transform infrared spectroscopy confirmed the presence of enzymes in the samples. Chitosan-based coatings were subsequently produced from the nanocomposites. Atomic force microscopy visualization revealed the formation of globular structures consisting of enzymes and carboxymethylcellulose on the halloysite surface. An analysis of the coatings revealed a uniform distribution of halloysite throughout the matrix. The antibacterial activity of the nanocomposite containing lysozyme against Escherichia coli OP 50-1 was 47.2% and 63.9% at a concentration of 0.5 and 1 mg/mL, respectively. The antibacterial activity of the nanocomposite containing trypsin against Escherichia coli OP 50-1 was 44.4 and 55.5% at concentrations of 0.5 and 1 mg/mL, respectively. The antibacterial activity of the nanocomposite containing lysozyme against Staphylococcus aureus 6583 was 26.1 and 50.7% at concentrations of 0.5 and 1 mg/mL, respectively. The antibacterial activity of the nanocomposite containing trypsin against Staphylococcus aureus 6583 was 53.6 and 75.4% at concentrations of 0.5 and 1 mg/mL, respectively. The antibacterial activity of coatings based on chitosan and the nanocomposites containing trypsin and lysozyme against Escherichia coli OP 50-1 and Staphylococcus aureus 6583 was observed. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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15 pages, 1917 KB

Open AccessArticle

Impact of Extrusion on Biofunctional, Rheological, Thermal, and Structural Properties of Corn Starch/Whey Protein Isolate Blends During In Vitro Gastrointestinal Digestion

by José A. Téllez-Morales, Jesús Rodríguez-Miranda, Fátima S. Serrano-Villa, Gustavo F. Gutiérrez-López, Reynold R. Farrera-Rebollo and Georgina Calderón-Domínguez

Polymers 2025, 17(23), 3211; https://doi.org/10.3390/polym17233211 - 2 Dec 2025

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Abstract

This study examines the effects of extrusion cooking on the biofunctional, rheological, thermal, and structural properties of corn starch (CS)/whey protein isolate (WPI) blends (100/0, 50/50, 0/100 w/w, both raw and extruded) during in vitro gastrointestinal digestion. Extrusion and in [...] Read more.

This study examines the effects of extrusion cooking on the biofunctional, rheological, thermal, and structural properties of corn starch (CS)/whey protein isolate (WPI) blends (100/0, 50/50, 0/100 w/w, both raw and extruded) during in vitro gastrointestinal digestion. Extrusion and in vitro digestion increased antioxidant activity (2,2′-Azino-Bis (3-Ethylbenzothiazoline-6-Sulfonic Acid) Diammonium Salt and 2,2-Diphenyl-1-Picrylhydrazyl). Extrusion improved the bioaccessibility of angiotensin-converting enzyme (ACE-1) inhibitory peptides, leading to high inhibition (>90%) in the intestinal phase across all samples, with this effect consistent between raw and extruded samples during digestion. The in vitro digestion process changes the rheological behavior of the samples, from a non-Newtonian fluid (dilatant) to a Newtonian fluid. Notably, extruded CS maintained pseudoplastic behavior across all phases. Thermally, extrusion resulted in complete gelatinization of CS and denaturation of WPI, as evidenced by the absence of endotherms. Structurally, extrusion induced unfolding of WPI α-helix and β-sheet regions, leading to the formation of β-turns and random coils, which could enhance enzyme accessibility. For CS, a decrease in the degree of double helix and order was observed, indicating an alteration of its ordered molecular structure. Additionally, the extrusion process slightly increased the amount of resistant starch. This work shows that extrusion generates antioxidant compounds by bioactive peptide release. Full article

(This article belongs to the Special Issue Functional Polymers for Food Industry)

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9 pages, 591 KB

Open AccessArticle

An Environmentally Benign Solvent for the Cationic Polymerization of Low Ceiling Temperature Polyaldehydes

by Jose C. Lopez Ninantay, Anthony C. Engler, Jared M. Schwartz and Paul A. Kohl

Polymers 2025, 17(23), 3210; https://doi.org/10.3390/polym17233210 - 2 Dec 2025

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Abstract

The synthesis of phthalaldehyde-based polymers has exclusively been carried out in dichloromethane, which causes environmental problems due to its halogen content and ozone-depleting attributes. In this study, an alternative solvent for the polymerization of o-phthalaldehyde-based polyaldehydes is disclosed. Ethyl acetate, a solvent [...] Read more.

The synthesis of phthalaldehyde-based polymers has exclusively been carried out in dichloromethane, which causes environmental problems due to its halogen content and ozone-depleting attributes. In this study, an alternative solvent for the polymerization of o-phthalaldehyde-based polyaldehydes is disclosed. Ethyl acetate, a solvent that is widely used in consumer products, dissolves a sufficient amount of reactants and polymer product at the reaction conditions, −86 °C, to provide a comparable yield to synthesis in dichloromethane. A significant learning from this study is that the reaction solvent does not have to fully dissolve all the reactants and products to produce stable polymer, compared to dichloromethane, which fully dissolves reactants and products. The polymer product precipitated from the ethyl acetate solution as the polymer formed. Although the reactants and products were not fully soluble in ethyl acetate, they retained sufficient mobility to allow the catalyst to initiate polymer chains and achieve molecular weights as high as 83.4 kg/mol. The synthesis of cyclic copolymers from o-phthalaldehyde and aliphatic aldehydes is also possible in ethyl acetate if the catalyst is added at a temperature below the ceiling temperature of the monomers and above the point where they crystallize from solution. Full article

(This article belongs to the Section Polymer Applications)

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19 pages, 8472 KB

Open AccessArticle

Tailoring the Properties of Soy Protein-Based Bioplastics via Plasticizer Composition and Extrusion Temperature for Controlled Iron Release

by Daniel Castro-Criado, Antonio J. Capezza, Alberto Romero and Mercedes Jiménez-Rosado

Polymers 2025, 17(23), 3209; https://doi.org/10.3390/polym17233209 - 2 Dec 2025

Viewed by 1653

Abstract

The development of sustainable bioplastic matrices for controlled micronutrient delivery represents a promising strategy in the agri-food and biomedical sectors. This study investigates the influence of plasticizer type (glycerol, water and their mixtures) and processing temperature (70–110 °C) on the fabrication and functional [...] Read more.

The development of sustainable bioplastic matrices for controlled micronutrient delivery represents a promising strategy in the agri-food and biomedical sectors. This study investigates the influence of plasticizer type (glycerol, water and their mixtures) and processing temperature (70–110 °C) on the fabrication and functional properties of extruded soy protein-based matrices for iron release. Results show that both the nature of the plasticizer and the extrusion temperature critically affect the microstructure and mechanical behavior of the matrices. Specifically, an intermediate glycerol/water ratio (50/50) during extrusion at 90 °C significantly improves matrix resistance, making it optimal for iron-controlled release. These findings underscore the crucial role of formulation and thermal parameters in engineering protein-based delivery systems, thereby paving the way for the design of next-generation biodegradable functional materials. Full article

(This article belongs to the Special Issue Valorization of Biopolymer from Renewable Biomass)

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1 pages, 327 KB

Open AccessCorrection

Correction: Ahn et al. Cellulose Nanocrystal Embedded Composite Foam and Its Carbonization for Energy Application. Polymers 2023, 15, 3454

by So Yeon Ahn, Chengbin Yu and Young Seok Song

Polymers 2025, 17(23), 3208; https://doi.org/10.3390/polym17233208 - 2 Dec 2025

Cited by 1 | Viewed by 247

Abstract

In the original publication [...] Full article

(This article belongs to the Section Polymer Applications)

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15 pages, 2388 KB

Open AccessArticle

Sustainable Composites from Recycled Polypropylene and Hazelnut Shell Flour for Application in Irrigation Systems

by Francesco Paolo La Mantia, Roberto Scaffaro, Giuseppe Balsamo, Carmelo Giuffré, Erica Gea Rodi, Simone Corviseri and Maria Clara Citarrella

Polymers 2025, 17(23), 3207; https://doi.org/10.3390/polym17233207 - 1 Dec 2025

Viewed by 461

Abstract

The irrigation sector urgently needs more eco-sustainable materials able to guarantee the same performance as traditional fittings manufactured from virgin fossil-based polymers. In this study, sustainable composites were developed by melt-compounding virgin and recycled polypropylene (RPP) with hazelnut shell (HS) powder with or [...] Read more.

The irrigation sector urgently needs more eco-sustainable materials able to guarantee the same performance as traditional fittings manufactured from virgin fossil-based polymers. In this study, sustainable composites were developed by melt-compounding virgin and recycled polypropylene (RPP) with hazelnut shell (HS) powder with or without maleic-anhydride-grafted polypropylene (PPC) coupling agent. The materials were characterized by a rheological and mechanical point of view. At high shear rates, the viscosity curves of matrices and composites converge, making the difference between neat and filled systems negligible in terms of processability. This indicates that standard injection-molding parameters used for the neat matrices can also be applied to the composites without significant adjustments. Tensile tests showed that adding 10 wt% HS powder increased the elastic modulus by approximately 30% (from 960 MPa to 1.2 GPa) while reducing elongation at break by about 90% compared with neat RPP. The use of PPC mitigated this loss of ductility, partially restoring tensile strength and increasing EB from 6% to 18% in RPP-based composites (+200%). Finally, sleeve bodies and nuts injection-molded from RPP/HS5 and RPP/HS5/PPC successfully resisted internal water pressure up to 3.5 bar without leakage or structural damage. These findings demonstrate that agro-industrial waste can be effectively valorized as a functional filler in recycled polypropylene, enabling the manufacture of irrigation fittings with mechanical and processing performances comparable to those of virgin PP and supporting the transition toward a circular economy. Full article

(This article belongs to the Special Issue Polymer Science and Technology: When Progress Meets Sustainability and Reliability)

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