Polymers

19 pages, 3260 KiB

Open AccessArticle

A Strategy Towards the Valorization of Aloe Vera Rinds to Obtain Crystalline Cellulose: Pretreatment Effects and Elemental Analysis

by Mayra Elizabeth Juárez Méndez, Diana Palma Ramírez, David Salvador García Zaleta, Karen A. Neri Espinoza, Acela López Benítez, Deyanira del Ángel López, Sandra Soledad Morales García and Helen Willcock

Polymers 2025, 17(4), 553; https://doi.org/10.3390/polym17040553 - 19 Feb 2025

Viewed by 513

Abstract

Although crystalline nanocellulose (CNCs) can be extracted from different resources, the employed pretreatments, which disrupt the inter- and intramolecular physical interactions, depend on the biomass sources. This study aims to valorize Aloe Vera (AV) rinds into cellulose and crystalline nanocellulose (CNC) employing two [...] Read more.

Although crystalline nanocellulose (CNCs) can be extracted from different resources, the employed pretreatments, which disrupt the inter- and intramolecular physical interactions, depend on the biomass sources. This study aims to valorize Aloe Vera (AV) rinds into cellulose and crystalline nanocellulose (CNC) employing two approaches during hydrolysis: sulfuric acid (CNC_SA) and citric acid (CNC_CA) after 30, 60, and 90 min of reaction. The effects of pretreatments and hydrolysis time on the functional groups and hydrogen bonding in biomass are discussed. Crystalline structure (polymorph type), crystallinity, thermal stability, morphology, particle size, and metal presence are also analyzed. A transformation from type I into II polymorph was achieved, where the intermolecular interactions governing cellulose were increased in CNC_SA and were almost maintained in CNC_CA. Properties based on the structure, thermal properties, particle size, and metal presence indicate that the CNC_SA30 and CNC_CA90 samples displayed potential application as reinforcement agents for other types of polymers having no more melting points of 160 and 220 °C, respectively. Full article

(This article belongs to the Special Issue Advanced Study on Natural Polymers and Their Applications)

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9 pages, 203 KiB

Open AccessEditorial

Polymeric Materials for Wastewater Treatment Applications

by Marta Otero and Ricardo N. Coimbra

Polymers 2025, 17(4), 552; https://doi.org/10.3390/polym17040552 - 19 Feb 2025

Viewed by 528

Abstract

Water of adequate quality is crucial for the survival of most life forms, playing a key role in human health, social and economic progress, and the functioning of ecosystems [...] Full article

(This article belongs to the Special Issue Polymeric Materials for Wastewater Treatment Applications)

16 pages, 4848 KiB

Open AccessArticle

Effects of Polymeric Crosslinker on Network Structure, Morphology, and Properties of Liquid Isoprene Rubber

by Jishnu Nirmala Suresh, Hans Liebscher, Hartmut Komber, Muhammad Tahir, Gerald Gerlach and Sven Wießner

Polymers 2025, 17(4), 551; https://doi.org/10.3390/polym17040551 - 19 Feb 2025

Viewed by 281

Abstract

In this study, we investigated the influence of an epoxy end-capped polypropylene oxide crosslinker (epoxy-PPO) on the formation of the crosslinked network structure, the stress–strain response, and the electro-mechanical actuation performance of a maleic anhydride functionalized liquid isoprene rubber (LIR). The crosslinker amount [...] Read more.

In this study, we investigated the influence of an epoxy end-capped polypropylene oxide crosslinker (epoxy-PPO) on the formation of the crosslinked network structure, the stress–strain response, and the electro-mechanical actuation performance of a maleic anhydride functionalized liquid isoprene rubber (LIR). The crosslinker amount varied from 10 (C-LIR-10) to 50 (C-LIR-50) weight parts per hundred parts (phr) of LIR. The swelling test of the cured rubbers revealed that C-LIR-20 formed the densest crosslinked network with the lowest chloroform uptake value within this series. The crosslinked rubber became stiffer in tensile response upon increasing the epoxy-PPO amount from C-LIR-10 to C-LIR-20 and then softened at higher amounts. The SEM measurements were used to relate this composition-induced softening of the rubbers to the phase morphology evolution from nanoscale homogeneity in C-LIR-10 to microscale segregations of excess crosslinkers in C-LIR-50. The use of epoxy-PPO improved the dielectric constant value of LIR; however, the leakage current through the films also increased from 25 µA DC to 320 µA DC for LIR-30 and LIR-50, respectively, during DEA operation. The electro-mechanical actuation tests with circular actuators showed that the C-LIR-10 elastomer film demonstrated a radial strain of 1.7% on activation at an electric field strength of 17.5 V/µm. At higher crosslinker amounts, the close proximity of excess epoxy-PPO molecules caused leakage current across elastomer films thus diminishing the actuation strain of otherwise relatively softer elastomers with higher dielectric constant values. Full article

(This article belongs to the Special Issue Process–Structure–Properties Relationships in Polymers and Polymer Composites)

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20 pages, 8363 KiB

Open AccessArticle

Predicting Stress–Strain Curve with Confidence: Balance Between Data Minimization and Uncertainty Quantification by a Dual Bayesian Model

by Tianyi Li, Zhengyuan Chen, Zhen Zhang, Zhenhua Wei, Gan-Ji Zhong, Zhong-Ming Li and Han Liu

Polymers 2025, 17(4), 550; https://doi.org/10.3390/polym17040550 - 19 Feb 2025

Viewed by 301

Abstract

Driven by polymer processing–property data, machine learning (ML) presents an efficient paradigm in predicting the stress–strain curve. However, it is generally challenged by (i) the deficiency of training data, (ii) the one-to-many issue of processing–property relationship (i.e., aleatoric uncertainty), and (iii) the unawareness [...] Read more.

Driven by polymer processing–property data, machine learning (ML) presents an efficient paradigm in predicting the stress–strain curve. However, it is generally challenged by (i) the deficiency of training data, (ii) the one-to-many issue of processing–property relationship (i.e., aleatoric uncertainty), and (iii) the unawareness of model uncertainty (i.e., epistemic uncertainty). Here, leveraging a Bayesian neural network (BNN) and a recently proposed dual-architected model for curve prediction, we introduce a dual Bayesian model that enables accurate prediction of the stress–strain curve while distinguishing between aleatoric and epistemic uncertainty at each processing condition. The model is trained using a Taguchi array dataset that minimizes the data size while maximizing the representativeness of 27 samples in a 4D processing parameter space, significantly reducing data requirements. By incorporating hidden layers and output-distribution layers, the model quantifies both aleatoric and epistemic uncertainty, aligning with experimental data fluctuations, and provides a 95% confidence interval for stress–strain predictions at each processing condition. Overall, this study establishes an uncertainty-aware framework for curve property prediction with reliable, modest uncertainty at a small data size, thus balancing data minimization and uncertainty quantification. Full article

(This article belongs to the Special Issue Simulation and Calculation of Polymer Composite Materials)

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25 pages, 4591 KiB

Open AccessArticle

Fabrication and Characterization of Buforin I-Loaded Electrospun Chitosan/Polyethylene Oxide Nanofibrous Membranes with Antimicrobial Activity for Food Packing Applications

by Sahar Roshanak, Hanieh Yarabbi, Jebraeil Movaffagh and Fakhri Shahidi

Polymers 2025, 17(4), 549; https://doi.org/10.3390/polym17040549 - 19 Feb 2025

Viewed by 271

Abstract

The rising resistance of bacteria to antibiotics has driven the search for new antimicrobial agents. This study focused on encapsulating Buforin I, an antimicrobial peptide, in chitosan/polyethylene oxide (CS-PEO) nanofibers. Buforin I was loaded at a minimum bactericidal concentration (MBC), 10× MBC, and [...] Read more.

The rising resistance of bacteria to antibiotics has driven the search for new antimicrobial agents. This study focused on encapsulating Buforin I, an antimicrobial peptide, in chitosan/polyethylene oxide (CS-PEO) nanofibers. Buforin I was loaded at a minimum bactericidal concentration (MBC), 10× MBC, and 20× MBC, with assessments on morphology, thermal properties, chemical bonds, crystalline structure, mechanical strength, antimicrobial activity, and cell toxicity. Techniques like differential scanning calorimetry and Fourier-transform infrared spectroscopy confirmed the effective loading of Buforin I in the nanofibers. Scanning electron microscopy showed that Buforin incorporation increased nanofiber diameters. The tensile strength peaked at 20× MBC. Microbial tests indicated that the inhibition zone for nanofibers at 20× MBC surpassed that of commercial antibiotics. Beef coated with CS-PEO nanofibers containing Buforin I demonstrated reduced pH and water activity, alongside lower weight loss during storage. Texture and color analyses revealed that the Buforin I nanofibers helped maintain beef hardness and slowed color degradation compared to control samples. Moreover, thiobarbituric acid levels and total microbial counts in the coated beef were significantly lower than controls (below 3 log CFU/g after 9 days at 4 °C). Thus, these nanofibers may serve as effective antimicrobial packaging agents to delay food spoilage. Full article

(This article belongs to the Special Issue Biopolymers for Food Packaging and Agricultural Applications)

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23 pages, 32809 KiB

Open AccessArticle

Synergistic Effect of Microbial-Induced Carbonate Precipitation Modified with Hydroxypropyl Methylcellulose on Improving Loess Disintegration and Seepage Resistance

by Xingyu Wang and Hong Sun

Polymers 2025, 17(4), 548; https://doi.org/10.3390/polym17040548 - 19 Feb 2025

Viewed by 328

Abstract

Microbial-induced carbonate precipitation (MICP) is an eco-friendly soil stabilization technique. This study explores the synergistic effects of incorporating hydroxypropyl methylcellulose (HPMC) into the MICP process to enhance the disintegration and seepage resistance of loess. A series of disintegration, seepage, scanning electron microscopy (SEM), [...] Read more.

Microbial-induced carbonate precipitation (MICP) is an eco-friendly soil stabilization technique. This study explores the synergistic effects of incorporating hydroxypropyl methylcellulose (HPMC) into the MICP process to enhance the disintegration and seepage resistance of loess. A series of disintegration, seepage, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests were conducted. The results show that HPMC forms protective membranes around calcium carbonate crystals produced by MICP and soil aggregates, which enhance cementation, reduce soluble salt dissolution, promote soil particle aggregation, and seal pore structures. At the optimal 0.4% HPMC dosage, the maximum accumulative disintegration percentage and the disintegration velocity decreased to zero. Additionally, HPMC-modified MICP reduced the amount, size, and flow velocity of seepage channels in loess. The integration of MICP with HPMC provides an efficient and sustainable solution for mitigating loess disintegration and seepage issues. Full article

(This article belongs to the Special Issue Structure, Characterization and Application of Bio-Based Polymers)

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18 pages, 13161 KiB

Open AccessArticle

Research on the Phenomenological Constitutive Relationship Model of Silicone Structural Adhesives for Glass Curtain Walls

by Nan Jin, Jianchao Zhao, Yuzhu Liang and Xiaoqing Zhao

Polymers 2025, 17(4), 547; https://doi.org/10.3390/polym17040547 - 19 Feb 2025

Viewed by 256

Abstract

Silicone structural adhesives (SSAs) play a critical role in load transfer within glass curtain wall systems. With the increasing service life of existing glass curtain walls in recent years, their structural safety has become a significant concern across various societal sectors. Accurate characterization [...] Read more.

Silicone structural adhesives (SSAs) play a critical role in load transfer within glass curtain wall systems. With the increasing service life of existing glass curtain walls in recent years, their structural safety has become a significant concern across various societal sectors. Accurate characterization of the stress–strain relationship of SSAs is fundamental for evaluating the safety and performance of curtain wall structures. While most existing studies rely on hyperelastic constitutive models derived from rubber materials, employing parameter fitting to describe the constitutive behavior of SSAs, there remains a notable lack of research directly addressing constitutive models tailored specifically for SSAs. Although SSAs share similar chemical compositions with rubber after curing, their mechanical properties exhibit substantial differences. As a result, conventional hyperelastic constitutive models often fail to adequately capture the diverse mechanical responses of SSAs. To address this gap, this study begins with a comprehensive market survey to identify and select representative SSAs. Tensile and shear mechanical experiments are then conducted, with the stress–strain relationships during loading processes accurately captured using advanced techniques, such as Digital Image Correlation (DIC). Building on the Acoustic Emission (AE) algorithm, an intelligent algorithm is developed to optimize the fitting of hyperelastic constitutive parameters, enabling a critical evaluation of the applicability of existing phenomenological hyperelastic models to SSAs. Furthermore, in response to the limitations of current models, a novel and universally applicable constitutive model for SSAs is proposed. The robustness of this model is rigorously validated through comparative analysis with experimental data. The findings of this study provide a universal phenomenological constitutive model for SSAs, significantly enhancing the efficiency and accuracy of constitutive relationship fitting for these materials. This advancement contributes to the improved design, assessment, and maintenance of glass curtain wall systems. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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12 pages, 7007 KiB

Open AccessArticle

The Structural Design of a New Graftable Antioxidant and the Theoretical Study of Its Role in the Cross-Linking Reaction Process of Polyethylene

by Yang Du, Hui Zhang, Chi Deng, Xia Du, Yan Shang, Xuan Wang, Qingguo Chen and Zesheng Li

Polymers 2025, 17(4), 546; https://doi.org/10.3390/polym17040546 - 19 Feb 2025

Viewed by 217

Abstract

Cross-linked polyethylene (XLPE) insulation is used in most advanced power cable technology. However, in traditional cross-linking, the conductivity of the cross-linking system sharply increases due to the presence of additives (antioxidants and cross-linked agents). Therefore, reducing the number of antioxidants to further reduce [...] Read more.

Cross-linked polyethylene (XLPE) insulation is used in most advanced power cable technology. However, in traditional cross-linking, the conductivity of the cross-linking system sharply increases due to the presence of additives (antioxidants and cross-linked agents). Therefore, reducing the number of antioxidants to further reduce conductivity is a very promising method. The structural design of a new dual-functional antioxidant 5-allyloxy-2-hydroxyl-3-tert-butylbenzophenone (5ATB) has been established. The antioxidant behavior and grafting reaction of 5ATB after photocatalysis under ultraviolet (UV) conditions were further studied using density functional theory (DFT). The reaction potential energy information of the six reaction channels at the B3LYP/6-311+G(d,p) level were obtained. The calculation results indicated that the reaction Gibbs energy barrier of 5ATB with O₂ is approximately 0.48 eV lower than that of the polyethylene chain with O₂ to achieve an anti-oxidative effect. Furthermore, the reaction-active site of 5ATB accepting H is located on the C of CH₂ in a C=C double bond, as demonstrated by an analysis of NBO charge populations. The proposed mechanism has the potential to further expand the design concept of insulation materials for advanced future power cables. Full article

(This article belongs to the Special Issue Theoretical and Computational Polymers Science: Physics, Chemistry and Biology)

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16 pages, 3025 KiB

Open AccessArticle

Electrochemical Biosensors by Means of Molecularly Imprinted Polymers (MIPs) Cortisol Recognition

by Jindapa Nampeng, Naphatsawan Vongmanee, Chuchart Pintavirooj, Wen-Tai Chiu and Sarinporn Visitsattapongse

Polymers 2025, 17(4), 545; https://doi.org/10.3390/polym17040545 - 19 Feb 2025

Viewed by 624

Abstract

Depression and anxiety are two common mental health issues that require serious attention, as they have significant impacts on human well-being, with both being emotionally and physically reflected in the increasing number of suicide cases globally. The World Health Organization (WHO) estimated that [...] Read more.

Depression and anxiety are two common mental health issues that require serious attention, as they have significant impacts on human well-being, with both being emotionally and physically reflected in the increasing number of suicide cases globally. The World Health Organization (WHO) estimated that about 322 million people around the world experienced mental illnesses in 2017, and this number continues to increase. Cortisol is a major stress-controlled hormone that is regulated by the hypothalamic–pituitary–adrenal (HPA) axis. The HPA axis has three main components, including the hypothalamus, pituitary gland, and adrenal gland, where cortisol, the primary stress hormone, is released. It plays crucial roles in responding to stress, energy balance, and the immune system. The cortisol level in the bloodstream usually increases when stress develops. Molecularly imprinted polymers (MIPs) have been highlighted in terms of creating artificial bioreceptors by mimicking the shape of detected biomolecules, making natural bioreceptor molecules no longer required. MIPs can overcome the limitations of chemicals and physical properties reducing over time and the short-time shelf life of natural bioreceptors. MIPs’ benefits are reflected in their ease of use, high sensitivity, high specificity, reusability, durability, and the lack of requirement for complicated sample preparation before use. Moreover, MIPs incur low costs in manufacturing, giving them a favorable budget for the market with simple utilization. MIPs can be formulated by only three key steps, including formation, the polymerization of functional monomers, and the creation of three-dimensional cavities mimicking the shape and size of targeting molecules. MIPs have a high potential as biosensors, especially working as bioanalytics for protein, anti-body, antigen, or bacteria detection. Herein, this research proposes an MIP-based cortisol biosensor in which cortisol is imprinted on methyl methacrylate (MMA) and methacrylic acid (MAA) produced by UV polymerization. This MIP-based biosensor may be an alternative method with which to detect and monitor the levels of hormones in biological samples such as serum, saliva, or urine due to its rapid detection ability, which would be of benefit for diagnosing depression and anxiety and prescribing treatment. In this study, quantitative detection was performed using an electrochemical technique to measure the changes in electrical signals in different concentrations of a cortisol solution ranging from 0.1 to 1000 pg/mL. The MIP-based biosensor, as derived by calculation, achieved its best detection limit of 1.035 pg/mL with a gold electrode. Tests were also performed on molecules with a similar molecular structure, including Medroxyprogesterone acetate and drospirenone, to ensure the sensitivity and accuracy of the sensors, demonstrating a low sensitivity and low linear response. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers: Design, Characterization and Application, 2nd Edition)

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17 pages, 5184 KiB

Open AccessArticle

Ultrashort Pulse Laser Fabrication and Evaluation of Innovative Resorbable Barbed Sutures

by Karuna Nambi Gowri, Walid Al Asad, Shubha Majumder, Xin Zhao and Martin William King

Polymers 2025, 17(4), 544; https://doi.org/10.3390/polym17040544 - 19 Feb 2025

Viewed by 251

Abstract

Laser micro-machining is a rapidly growing technique to create, manufacture and fabricate microstructures on different materials ranging from metals and ceramics to polymers. Micro- and nano-machining on different materials has been helpful and useful for various biomedical applications. This study focuses on the [...] Read more.

Laser micro-machining is a rapidly growing technique to create, manufacture and fabricate microstructures on different materials ranging from metals and ceramics to polymers. Micro- and nano-machining on different materials has been helpful and useful for various biomedical applications. This study focuses on the micro-machining of innovative barbed sutures using an ultrashort pulse laser, specifically a femtosecond (fs) laser system. Two bioresorbable polymeric materials, namely, catgut and poly (4-hydroxybutyrate) (P4HB), were studied and micro-machined using the femtosecond (fs) laser system. The optimized laser parameter was used to fabricate two different barb geometries, namely, straight and curved barbs. The mechanical properties were evaluated via tensile testing, and the anchoring performance was studied by means of a suture–tissue pull-out protocol using porcine dermis tissue which was harvested from the medial dorsal site. Along with the evaluation of the mechanical and anchoring properties, the thermal characteristics and degradation profiles were assessed and compared against mechanically cut barbed sutures using a flat blade. The mechanical properties of laser-fabricated barbed sutures were significantly improved when compared to the mechanical properties of the traditionally/mechanically cut barbed sutures, while there was not any significant difference in the anchoring properties of the barbed sutures fabricated through either of the fabrication techniques. Based on the differential scanning calorimetry (DSC) results for thermal transitions, there was no major impact on the inherent material properties due to the laser treatment. This was also observed in the degradation results, where both the mechanically cut and laser-fabricated barbed sutures exhibited similar profiles throughout the evaluation time period. It was concluded that switching the fabrication technique from mechanical cutting to laser fabrication would be beneficial in producing a more reproducible and consistent barb geometry with more precision and accuracy. Full article

(This article belongs to the Topic Advanced Biomaterials: Processing and Applications)

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15 pages, 2219 KiB

Open AccessArticle

Anion-Exchange Strategy for Ru/RuO₂-Embedded N/S-Co-Doped Porous Carbon Composites for Electrochemical Nitrogen Fixation

by Shahzeb Ali Samad, Xuanzi Ye, Zhiya Han, Senhe Huang, Chenbao Lu, Junbo Hou, Min Yang, Zhenyu Zhang, Feng Qiu and Xiaodong Zhuang

Polymers 2025, 17(4), 543; https://doi.org/10.3390/polym17040543 - 19 Feb 2025

Viewed by 359

Abstract

Ionic porous polymers have been widely utilized efficiently to anchor various metal atoms for the preparation of metal-embedded heteroatom-doped porous carbon composites as the active materials for electrocatalytic applications. However, the rational design of the heteroatom and metal elements in HPC-based composites remains [...] Read more.

Ionic porous polymers have been widely utilized efficiently to anchor various metal atoms for the preparation of metal-embedded heteroatom-doped porous carbon composites as the active materials for electrocatalytic applications. However, the rational design of the heteroatom and metal elements in HPC-based composites remains a significant challenge, due to the tendency of the aggregation of metal nanoparticles during pyrolysis. In this study, a nitrogen (N)- and sulfur (S)-enriched ionic covalent organic framework (iCOF) incorporating viologen and thieno[3,4-b] thiophene (TbT) was constructed via Zincke-type polycondensation. The synthesized iCOF possesses a crystalline porous structure with a pore size of 3.05 nm, a low optical band gap of 1.88 eV, and superior ionic conductivity of 10^−2.672 S cm⁻¹ at 333 K, confirming the ionic and conjugated nature of our novel iCOF. By applying the iCOF as the precursor, a ruthenium and ruthenium(IV) oxide (Ru/RuO₂) nanoparticle-embedded N/S-co-doped porous carbon composite (NSPC-Ru) was prepared by using a two-step sequence of anion-exchange and pyrolysis processes. In the electrochemical nitrogen reduction reaction (eNRR) application, the NSPC-Ru achieves an impressive NH₃ yield rate of 32.0 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 13.2% at −0.34 V vs. RHE. Thus, this innovative approach proposes a new route for the design of iCOF-derived metal-embedded porous carbon composites for enhanced NRR performance. Full article

(This article belongs to the Section Polymer Chemistry)

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32 pages, 6117 KiB

Open AccessReview

Toward Intelligent Materials with the Promise of Self-Healing Hydrogels in Flexible Devices

by Han-Seop Song, Md. Mahamudul Hasan Rumon, Mohammad Mizanur Rahman Khan and Jae-Ho Jeong

Polymers 2025, 17(4), 542; https://doi.org/10.3390/polym17040542 - 19 Feb 2025

Viewed by 633

Abstract

Flexible sensors are revolutionizing wearable and implantable devices, with conductive hydrogels emerging as key materials due to their biomimetic structure, biocompatibility, tunable transparency, and stimuli-responsive electrical properties. However, their fragility and limited durability pose significant challenges for broader applications. Drawing inspiration from the [...] Read more.

Flexible sensors are revolutionizing wearable and implantable devices, with conductive hydrogels emerging as key materials due to their biomimetic structure, biocompatibility, tunable transparency, and stimuli-responsive electrical properties. However, their fragility and limited durability pose significant challenges for broader applications. Drawing inspiration from the self-healing capabilities of natural organisms like mussels, researchers are embedding self-repair mechanisms into hydrogels to improve their reliability and lifespan. This review highlights recent advances in self-healing (SH) conductive hydrogels, focusing on synthesis methods, healing mechanisms, and strategies to enhance multifunctionality. It also explores their wide-ranging applications, including in vivo signal monitoring, wearable biochemical sensors, supercapacitors, flexible displays, triboelectric nanogenerators, and implantable bioelectronics. While progress has been made, challenges remain in balancing self-healing efficiency, mechanical strength, and sensing performance. This review offers insights into overcoming these obstacles and discusses future research directions for advancing SH hydrogel-based bioelectronics, aiming to pave the way for durable, high-performance devices in next-generation wearable and implantable technologies. Full article

(This article belongs to the Special Issue Advanced Polymer Composites for Supercapacitors and Sensors)

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19 pages, 2724 KiB

Open AccessArticle

Carbon Molecular Sieve Membranes from Acenaphthenequinone–Biphenyl Polymer; Synthesis, Characterization, and Effect on Gas Separation and Transport Properties

by Jesús Ortiz-Espinoza, Olivia Hernández-Cruz, Mikhail Zolotukhin, F. Alberto Ruiz-Treviño, María Isabel Loría-Bastarrachea and Manuel Aguilar-Vega

Polymers 2025, 17(4), 541; https://doi.org/10.3390/polym17040541 - 19 Feb 2025

Viewed by 390

Abstract

A rigid, high temperature-resistant aromatic polymer, poly(1,1′-biphenyl)-6,8a-dihydroacenaphthylene-1(2H)-one (BDA) comprising acenaphthenequinone and biphenyl was successfully synthesized by superacid catalyzed polymerization. BDA has a high decomposition temperature (T_d = 520 °C) that renders it a viable candidate for carbon molecular sieve membranes (CMSM) formation. [...] Read more.

A rigid, high temperature-resistant aromatic polymer, poly(1,1′-biphenyl)-6,8a-dihydroacenaphthylene-1(2H)-one (BDA) comprising acenaphthenequinone and biphenyl was successfully synthesized by superacid catalyzed polymerization. BDA has a high decomposition temperature (T_d = 520 °C) that renders it a viable candidate for carbon molecular sieve membranes (CMSM) formation. BDA precursor pyrolysis at 600 °C (BDA-P600) leads to a carbon turbostratic structure formation with graphene-like amorphous strands in a matrix with micropores and ultramicropores, resulting in a carbon structure with higher diffusion and higher selectivity than dense BDA. When the BDA pyrolysis temperature is raised to 700 °C (BDA-P700), the average stacking number of carbon layers N increases, along with an increase in the crystallite thickness stacking L_c, and layer plane size L_a, leading to a more compact structure. Pure gas permeability coefficients P are between 3 and 5 times larger for BDA-P600 compared to the BDA precursors. On the other hand, there is a P decrease between 10 and 50% for O₂ and CO₂ between CMSM BDA-P600 and BDA-P700, while the large kinetic diameter gases N₂ and CH₄ show a large decrease in permeability of 44 and 67%, respectively. It was found that the BDA-P700 WAXD results show the emergence of a new peak at 2θ = 43.6° (2.1 Å), which effectively hinders the diffusion of gases such O₂, N₂, and CH₄. This behavior has been attributed to the formation of new micropores that become increasingly compact at higher pyrolysis temperatures. As a result, the CMSM derived from BDA precursors pyrolyzed at 700 °C (BDA-P700) show exceptional O₂/N₂ gas separation performance, significantly surpassing baseline trade-off limits. Full article

(This article belongs to the Special Issue Development of High-Performance Polymers for Membranes Applied to Gas and Liquid Separations)

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17 pages, 5614 KiB

Open AccessArticle

Revealing the Calcium Assisted Partial Catalytic Graphitization of Lignin-Derived Hard Carbon Anode and Its Electrochemical Behaviors in Sodium Ion Batteries

by Jungpil Kim, Sang-Hyun Lee and Junghoon Yang

Polymers 2025, 17(4), 540; https://doi.org/10.3390/polym17040540 - 19 Feb 2025

Viewed by 331

Abstract

Among the various contenders for next-generation sodium-ion battery anodes, hard carbons stand out for their notable reversible capacity, extended cycle life, and cost-effectiveness. Their economic advantage can be further enhanced by using inexpensive precursors, such as biomass waste. Lignin, one of the most [...] Read more.

Among the various contenders for next-generation sodium-ion battery anodes, hard carbons stand out for their notable reversible capacity, extended cycle life, and cost-effectiveness. Their economic advantage can be further enhanced by using inexpensive precursors, such as biomass waste. Lignin, one of the most abundant natural biopolymers on Earth, which can be readily obtained from wood, possesses a three-dimensional amorphous polymeric structure, making it a suitable candidate for producing carbonaceous materials through appropriate carbonization processes for energy storage applications. In this work, we synthesized hard carbon using lignin containing CaSO₄ to facilitate partial catalytic graphitization to improve the microstructural features, such as interlayer spacing, degree of disorder, and surface defects. Partial catalytic graphitization enables hard carbon to develop an ordered structure compared with hard carbon carbonized without CaSO₄ as analyzed by X-ray diffraction, Raman spectroscopy, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy. The CaSO₄-aided partially catalytic graphitized hard carbon (CCG-HC) exhibited improved electrochemical performance, showing a larger portion of the low-voltage plateau—an indicator typically associated with a highly ordered structure—compared to simply carbonized hard carbon (HC). Notably, CCG-HC delivered a reversible capacity of 237 mAh g⁻¹, retained 95.6% of its capacity over 100 cycles at 50 mA g⁻¹, and exhibited 127 mAh g⁻¹ at 1.0 A g⁻¹. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Electroactive Polymers: 2nd Edition)

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22 pages, 3286 KiB

Open AccessArticle

Background of New Measurement Electronic Devices with Polyelectrolyte Hydrogel Base

by Kaisarali Kadyrzhan, Ibragim Suleimenov, Lyazat Tolymbekova, Gaini Seitenova and Eldar Kopishev

Polymers 2025, 17(4), 539; https://doi.org/10.3390/polym17040539 - 19 Feb 2025

Viewed by 268

Abstract

It has been demonstrated that when a low-molecular-weight salt solution flows through a polyelectrolyte gel, an electromotive force is generated, and its polarity depends on the sign of the polyelectrolyte network’s charge. A mathematical model proving the possibility of developing a device for [...] Read more.

It has been demonstrated that when a low-molecular-weight salt solution flows through a polyelectrolyte gel, an electromotive force is generated, and its polarity depends on the sign of the polyelectrolyte network’s charge. A mathematical model proving the possibility of developing a device for separating a solution of low-molecular salt into enriched and depleted phases under the influence of gravitational forces has been developed. Such a device contains a system of parallel columns filled with different kinds of cross-linked polyelectrolyte networks. The proposed mathematical model is grounded in the theory of double electrical layers forming at the hydrogel/solution interface; these layers deform under non-equilibrium conditions, specifically during the flow of the solution through the cross-linked polyelectrolyte network. An analogous model is proposed describing the case of an analogous device based on an electric current passing through two oppositely charged contacting networks, which provides the possibility of separating the initial solution into enriched and the depleted phases too. The practical applications of the found effect are discussed. In particular, it is demonstrated that a wide number of measurement electronic devices can be created on such a base, including devices to be used within the investigation of polyelectrolyte hydrogels of different types. Full article

(This article belongs to the Section Polymer Networks)

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23 pages, 5013 KiB

Open AccessArticle

Study on the Impact of Diluent Dosages on the Epoxy–Polythiol Self-Healing System

by Jiajia Sheng, Yang Guo, Xin Pang, Wenjing Ma, Hailu Yang, Yalin Liu, Linbing Wang and Shanglin Song

Polymers 2025, 17(4), 538; https://doi.org/10.3390/polym17040538 - 19 Feb 2025

Viewed by 298

Abstract

Self-healing technology is an effective method for enhancing the crack resistance of cement-based composites. This study focuses on the impact of the environmentally friendly diluent C12-14 alkyl glycidyl ether (AGE) on the performance of the epoxy resin–polythiol (rimethylolpropane tris (3-mercaptopropionate), TMPMP) self-healing system, [...] Read more.

Self-healing technology is an effective method for enhancing the crack resistance of cement-based composites. This study focuses on the impact of the environmentally friendly diluent C12-14 alkyl glycidyl ether (AGE) on the performance of the epoxy resin–polythiol (rimethylolpropane tris (3-mercaptopropionate), TMPMP) self-healing system, examining core fluidity, microcapsule properties, molecular dynamics, and the mechanical properties of cured products. The results show that as the AGE dosage increases, the particle size distribution of microcapsules becomes more concentrated, and the dispersion of particles is improved. Fourier-transform infrared spectroscopy confirms the successful encapsulation of E-51 and AGE. Microcapsules maintain structural integrity at high temperatures of 423.15 K. The onset thermal degradation temperature of the mixture shows an increasing trend with reduced AGE dosage. Specifically, TMPMP_35% exhibits an onset degradation temperature of 370.95 K, while that of TMPMP_20% is increased by 57.57% compared to TMPMP_35%. Conversely, the initial and peak temperatures of the curing reaction decrease with less AGE incorporation. Thermodynamic analysis reveals that activation energy (E) initially increases and then decreases with increasing AGE. The frequency factor (A) correlates positively with the heating rate, indicating that the curing reaction’s reactivity is closely linked to heating rate. Minor variations in the reaction rate constant (k) indicate that the self-healing system maintains stable reactive activity at low temperatures. Notably, the AGE dosage significantly affects the rigidity of the self-healing system; the average Young’s modulus inversely correlates with AGE dosage, with the most substantial decrease of 5.88% occurring when AGE increases from 30% to 35%. This study offers insights into optimizing diluent ratios to balance self-healing and mechanical properties, essential for developing high-performance self-healing cement materials. Full article

(This article belongs to the Section Smart and Functional Polymers)

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14 pages, 3133 KiB

Open AccessArticle

Enhanced Electrothermal Properties of Core–Sheath Lignin-Derived Carbon Nanotube Yarns with UHMWPE Insulation

by Hongmei Dai, Chao Jia, Zexu Hu, Senlong Yu, Hengxue Xiang, Xuefen Wang and Meifang Zhu

Polymers 2025, 17(4), 537; https://doi.org/10.3390/polym17040537 - 19 Feb 2025

Viewed by 302

Abstract

A critical challenge in wearable electrothermal textiles is achieving effective insulation while maintaining sheath flexibility, which is essential for enhancing the mechanical properties and durability of conductive materials under everyday conditions, such as washing, stretching, and twisting. In this work, we employ a [...] Read more.

A critical challenge in wearable electrothermal textiles is achieving effective insulation while maintaining sheath flexibility, which is essential for enhancing the mechanical properties and durability of conductive materials under everyday conditions, such as washing, stretching, and twisting. In this work, we employ a coaxial tubular braiding technique to coat a high-conductivity carbon nanotube (CNT) yarn with a high-strength insulation layer made of ultra-high-molecular-weight polyethylene (UHMWPE) multifilaments, resulting in a core–sheath-structure CNT yarn with excellent electrothermal performance. By adjusting the number of UHMWPE multifilaments and the sheath braiding angle, we achieve high flexibility, high tensile strength, and abrasion and wash resistance, as well as improved electrical stability for the CNT yarns. Additionally, the CNT yarns with an insulation layer effectively prevent short-circuiting during use and achieve superior thermal management, with a significant increase in steady-state temperature under operational conditions, exhibiting significant potential for applications in wearable electronic devices. Full article

(This article belongs to the Section Polymer Applications)

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26 pages, 7894 KiB

Open AccessArticle

Advanced Nanobiocomposite Hydrogels Incorporating Organofunctionalized LDH for Soft Tissue Engineering Applications

by Ionut-Cristian Radu, Eugenia Tanasa, Sorina Dinescu, George Vlasceanu and Catalin Zaharia

Polymers 2025, 17(4), 536; https://doi.org/10.3390/polym17040536 - 19 Feb 2025

Viewed by 327

Abstract

Nanocomposite hydrogels are gaining significant attention for biomedical applications in soft tissue engineering due to the increasing demand for highly flexible and durable soft polymer materials. This research paper focused on investigating and optimizing a procedure for the development of novel nanocomposite hydrogels [...] Read more.

Nanocomposite hydrogels are gaining significant attention for biomedical applications in soft tissue engineering due to the increasing demand for highly flexible and durable soft polymer materials. This research paper focused on investigating and optimizing a procedure for the development of novel nanocomposite hydrogels based on poly(2-hydroxyethyl methacrylate)-co-(2-acrylamido-2-methylpropane sulfonic acid) (HEMA/AMPSA) copolymers. These hydrogels were synthesized through a grafting-through process, where the polymer network was formed using a modified clay crosslinker. The layered double hydroxide (LDH) clay modified with 3-(trimethoxysilyl)propyl methacrylate (ATPM) was synthesized using a novel recipe through a two-step procedure. The nanocomposite hydrogel compositions were optimized to achieve soft hydrogels with high flexibility. The developed materials were analyzed for their mechanical and morphological properties using tensile and compressive tests, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and micro-computed tomography (micro-CT). The swelling behavior, network density, and kinetic diffusion mechanism demonstrated the specific characteristics of the materials. The modified LDH-ATPM was further characterized using Thermogravimetry (TGA), FTIR-ATR and X-ray diffraction (XRD). Biological assessments on human adipose-derived stem cells (hASCs) were essential to evaluate the biocompatibility of the nanocomposite hydrogels and their potential for soft tissue applications. Full article

(This article belongs to the Section Polymer Applications)

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15 pages, 5375 KiB

Open AccessArticle

Changes in Heat Resistance and Mechanical Properties of Peroxide Cross-Linking HDPE: Effects of Compounding Cross-Linkers

by Shunquan Liu, Run Zhang, Chenchao Fu, Tianshuo Zheng and Ping Xue

Polymers 2025, 17(4), 535; https://doi.org/10.3390/polym17040535 - 19 Feb 2025

Viewed by 340

Abstract

Due to excellent chemical resistance and impermeability, high-density polyethylene (HDPE) is widely used in petrochemical transportation, product packaging, sports equipment, and marine applications. Yet, with the wide variety of service environments, its mechanical and thermal properties do not meet the demand. In the [...] Read more.

Due to excellent chemical resistance and impermeability, high-density polyethylene (HDPE) is widely used in petrochemical transportation, product packaging, sports equipment, and marine applications. Yet, with the wide variety of service environments, its mechanical and thermal properties do not meet the demand. In the present study, a compounding cross-linker comprising di-tert-butyl peroxide (DTBP) and triallyl isocyanurate (TAIC) is employed by combining with a two-step preparation process. High-quality cross-linking reactions are achieved for HDPE. In this study, the cross-linking of DTBP is first examined separately. A peak cross-linking degree of 74.7% is achieved, and there is a large improvement in thermal resistance and mechanical properties. Subsequently, the composite cross-linking system of DTBP and TAIC is investigated. The peak cross-linking degree is 82.1% (10% increase compared to DTBP). The peak heat deformation temperature is 80.1 °C (22% increase compared to DTBP). The peak impact strength is 104.73 kJ/m² (207% increase compared to neat HDPE). The flexural strength is 33.6 MPa (22% increase compared to neat HDPE). The results show that this cross-linking system further improves the cross-linking degree, heat resistance, and mechanical properties of HDPE, indicating its potential application in engineering materials for high performance. Full article

(This article belongs to the Special Issue Advances in Polymer Composites II)

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37 pages, 14520 KiB

Open AccessArticle

Computational and Experimental Ballistic Behavior of Epoxy Composites Reinforced with Carnauba Fibers: A Stand-Alone Target and Multilayered Armor System

by Raí Felipe Pereira Junio, Bernardo Soares Avila de Cêa, Douglas Santos Silva, Édio Pereira Lima Júnior, Sergio Neves Monteiro and Lucio Fabio Cassiano Nascimento

Polymers 2025, 17(4), 534; https://doi.org/10.3390/polym17040534 - 19 Feb 2025

Viewed by 355

Abstract

The development of efficient and sustainable armor systems is crucial for protecting bodies and vehicles. In this study, epoxy composites reinforced with natural lignocellulosic fibers (NLFs) from carnauba (Copernicia prunifera) were produced with 0, 10, 20, 30, and 40% fiber volume [...] Read more.

The development of efficient and sustainable armor systems is crucial for protecting bodies and vehicles. In this study, epoxy composites reinforced with natural lignocellulosic fibers (NLFs) from carnauba (Copernicia prunifera) were produced with 0, 10, 20, 30, and 40% fiber volume fractions. Their ballistic performance was evaluated by measuring residual velocity and absorbed energy after impact with 7.62 mm ammunition, as well as their application in a multilayer armor system (MAS). Scanning electron microscopy (SEM) was used to analyze fracture regions, and explicit dynamic simulations were performed for comparison with experimental tests. Residual velocity tests indicated a limit velocity (V_L) between 213 and 233 m/s and absorbed energy (E_abs) between 221 and 264 J, surpassing values reported for aramid fabric. All formulations showed indentation depths below the National Institute of Justice (NIJ) limit, with the 40% fiber sample achieving the lowest depth (31.2 mm). The simulation results correlated well with the experimental data, providing insight into deformation mechanisms during a level III ballistic event. These findings demonstrate the high potential of carnauba fibers in epoxy-based polymer composites, particularly as an intermediate layer in MAS, offering a sustainable alternative for ballistic protection. Full article

(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications, 3rd Edition)

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19 pages, 6699 KiB

Open AccessArticle

Influence of Electron Beam Irradiation and RPMI Immersion on the Development of Magnesium-Doped Hydroxyapatite/Chitosan Composite Bioactive Layers for Biomedical Applications

by Andreea Groza, Maria E. Hurjui, Sasa A. Yehia-Alexe, Cornel Staicu, Coralia Bleotu, Simona L. Iconaru, Carmen S. Ciobanu, Liliana Ghegoiu and Daniela Predoi

Polymers 2025, 17(4), 533; https://doi.org/10.3390/polym17040533 - 18 Feb 2025

Viewed by 385

Abstract

Magnesium-doped hydroxyapatite/chitosan composite coatings produced by the radio-frequency magnetron sputtering technique were exposed to 5 MeV electron beams of 8 and 30 Gy radiation doses in a linear electron accelerator. The surfaces of unirradiated layers are smooth, while the irradiated ones exhibit nano-structures [...] Read more.

Magnesium-doped hydroxyapatite/chitosan composite coatings produced by the radio-frequency magnetron sputtering technique were exposed to 5 MeV electron beams of 8 and 30 Gy radiation doses in a linear electron accelerator. The surfaces of unirradiated layers are smooth, while the irradiated ones exhibit nano-structures with sizes that increase from 60 nm at a 8 Gy dose to 200 nm at a 30 Gy dose. Young’s modulus and the stiffness of the layers decrease from 58.9 GPa and 10 µN/nm to 5 GPa and 2.2 µN/nm, respectively, when the radiation doses are increased from 0 to 30 Gy. These data suggest the diminishing of the contribution of the chitosan to the elasticity of the magnesium-doped hydroxyapatite/chitosan composite layers after electron beam irradiation. The biological capabilities of the coatings were assessed before and after their immersion in RPMI-1640 cell culture medium for 7 and 14 days, respectively, and further cultured with a MG63 cell line (ATCC CRL1427) in Dulbecco’s Modified Eagle Medium supplemented with fetal bovine serum, penicillin–streptomycin, and L-glutamine. Thus, 1 µm spherical structures were developed on the surfaces of the layers exposed to a 30 Gy radiation dose and immersed for 14 days in the RPMI-1640 biological medium. The molecular structures of all the RPMI-1640 immersed samples were modified by the growth of a carbonated hydroxyapatite layer characterized by a B-type substitution, as Fourier Transform Infrared Spectroscopy revealed. The biological assay proved the increased biocompatibility of the layers kept in RPMI-1640 medium and enhanced MG63 cell attachment and proliferation. Atomic force microscopy analysis indicated the elongated fibroblastic cell morphology of MG63 cells with minor alteration at 30 Gy irradiation doses as a result of layer biocompatibility modifications. Full article

(This article belongs to the Special Issue Advanced Polymer Materials in Drug Delivery and Tissue Engineering Applications)

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17 pages, 11757 KiB

Open AccessArticle

Mechanical Performance Enhancement in Natural Fibre-Reinforced Thermoplastic Composites Through Surface Treatment and Matrix Functionalisation

by Ângela Pinto, Dina Esteves, Luís Nobre, João Bessa, Fernando Cunha and Raúl Fangueiro

Polymers 2025, 17(4), 532; https://doi.org/10.3390/polym17040532 - 18 Feb 2025

Viewed by 443

Abstract

This study aims to investigate the behaviour of thermoplastic composites reinforced with natural fibres. Composite materials were developed using reactive methyl methacrylate (MMA) resin, commercially known as Elium^® (Arkema, Colombes, France), with the incorporation of cellulose nanocrystals (CNCs), dispersed in the matrix [...] Read more.

This study aims to investigate the behaviour of thermoplastic composites reinforced with natural fibres. Composite materials were developed using reactive methyl methacrylate (MMA) resin, commercially known as Elium^® (Arkema, Colombes, France), with the incorporation of cellulose nanocrystals (CNCs), dispersed in the matrix at different concentrations. Natural fibres, such as flax, were chemically treated by immersion in an aqueous solution based on NaHCO₃, during different periods of exposure. After this treatment, flax fibres were washed with distilled water and dried. The degree of fibre surface tension was measured in terms of the contact angle. Then, cellulose nanocrystals were incorporated and mixed in the thermoplastic resin, and the samples were developed via the incorporation of intercalated layers of treated flax fibres. The composites were produced using compression moulding. After that, the samples were evaluated, regarding their mechanical performance and morphology. The research results show that flax fibres treated with 9 wt. % NaHCO₃ for 48 h had improved flexural strength as a result of removing impurities and exposing hydroxyl groups that react with Na⁺ ions present in NaHCO₃, which enhances its mechanical properties. The incorporation of 1% CNCs into thermoplastic resin significantly enhanced the fibre/matrix interface, resulting in a remarkable 38% increase in flexural strength. These findings demonstrate the effectiveness of using treated natural fibres and CNCs to improve composites’ performance. Full article

(This article belongs to the Special Issue Polymer Materials and Polymer Composites—on the Way to Sustainable Development)

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15 pages, 4231 KiB

Open AccessArticle

Microstructure and Release Behavior of Alginate–Natural Hydrocolloid Composites: A Comparative Study

by Hatice Sıçramaz, Ali Baran Dönmez, Buse Güven, Derya Ünal and Elif Aşbay

Polymers 2025, 17(4), 531; https://doi.org/10.3390/polym17040531 - 18 Feb 2025

Viewed by 344

Abstract

This study investigated the effects of combining sodium alginate (ALG) with various natural hydrocolloids on the microstructure and release behaviors of microbeads. The encapsulation solutions were prepared at a 1:1 (w/w) ratio with ALG as the control and carrageenan [...] Read more.

This study investigated the effects of combining sodium alginate (ALG) with various natural hydrocolloids on the microstructure and release behaviors of microbeads. The encapsulation solutions were prepared at a 1:1 (w/w) ratio with ALG as the control and carrageenan (CAR), locust bean gum (LBG), acacia gum (ACA), pectin (PEC), and carboxymethyl cellulose (CMC) as experimental groups. Each formulation contained 0.2% (w/v) tartrazine and was extruded into a CaCl₂ solution for bead production. Encapsulation efficiency varied across formulations, with the lowest in the control (ALG-ALG) and highest in ALG-CAR and ALG-CMC, reaching 74% and 78%, respectively. The microbead sizes ranged from 2.07 to 3.48 mm, with the lowest particle diameter observed in ALG-ACA composites. Surface analysis showed smooth and uniform microbeads in the control (ALG-ALG), while ALG-LBG microbeads were rougher. Release kinetics were assessed using various models, with the Higuchi model best describing the release for most formulations (highest R² values). Tartrazine release followed pseudo-Fickian behavior in all formulations, with slower release in ALG-ACA and faster release in ALG-LBG microbeads. This study fills a gap in understanding how the incorporation of different natural hydrocolloids influences both the encapsulation efficiency and release dynamics of alginate-based microbeads, providing valuable insights for applications in food and pharmaceutical industries. Full article

(This article belongs to the Special Issue Development of Polymer Materials as Functional Coatings)

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14 pages, 5644 KiB

Open AccessArticle

Comprehensive Performance Regulation and Characterization of Polypropylene/Elastomer Composite Insulation Materials

by Xinhua Dong, Xianhao Fan and Wei Wang

Polymers 2025, 17(4), 530; https://doi.org/10.3390/polym17040530 - 18 Feb 2025

Viewed by 279

Abstract

Polypropylene (PP) represents an important development direction for recyclable cable insulation materials. This paper investigates the synergistic improvement mechanism of the mechanical and electrical properties of PP. The effect of elastomers on the aggregation structure and carrier migration of the samples was investigated [...] Read more.

Polypropylene (PP) represents an important development direction for recyclable cable insulation materials. This paper investigates the synergistic improvement mechanism of the mechanical and electrical properties of PP. The effect of elastomers on the aggregation structure and carrier migration of the samples was investigated by analyzing the microstructure, crystallization, and mechanical and electrical properties of PP/elastomer composites. The results show that elastomers can reduce the tensile modulus of PP, while improving the tensile strength and elongation at break, thereby enhancing the mechanical properties of PP. The elastomer and the PP matrix have better compatibility and introduce amorphous regions, generating a large number of crystalline–amorphous interfaces, which introduce deep traps and reduce the mobility of carriers. Meanwhile, with an increase in elastomer content, the breakdown strength and volume resistivity both increase and then decrease. Among the samples tested, PP/PBE-2 has the best electrical properties and is the insulation material with the best mechanical and electrical properties. This study provides an important reference for the comprehensive performance regulation of PP insulation materials for high-voltage cables. Full article

(This article belongs to the Section Smart and Functional Polymers)

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15 pages, 5877 KiB

Open AccessArticle

Impact of Surfactants on Silk Fibroin Self-Assembly at the Air–Water Interface

by O. Yu. Milyaeva, R. Miller, G. Loglio, A. R. Rafikova, Z. Wan and B. A. Noskov

Polymers 2025, 17(4), 529; https://doi.org/10.3390/polym17040529 - 18 Feb 2025

Viewed by 311

Abstract

Silk fibroin (SF)-based materials attract significant interest because of their biocompability and great diversity of possible morphologies. One of the approaches to obtain SF materials is the use of an air–water or oil–water interface as a template for protein self-assembly. Surfactants can change [...] Read more.

Silk fibroin (SF)-based materials attract significant interest because of their biocompability and great diversity of possible morphologies. One of the approaches to obtain SF materials is the use of an air–water or oil–water interface as a template for protein self-assembly. Surfactants can change the surface properties of adsorbed SF layers by promoting or preventing the formation of SF fiber networks. This study focuses on the influence of two typical ionic surfactants, cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS), on the dynamic properties of SF layers adsorbed at the air–water interface. The dynamic surface elasticity, surface tension, ellipsometric angle Δ, and the film thickness were measured as a function of the surface age and surfactant concentration. The morphology of the layers was evaluated by atomic force microscopy (AFM). For the adsorption layers of globular proteins, the main effect of the surfactants consists in the protein unfolding at high concentrations and in a decrease in the electrostatic adsorption barrier. In the case of SF layers, CTAB and SDS strongly influence the protein aggregation at the air–water interface. Regardless of the sign of the surfactant charge, its addition to SF solutions results in a decrease in the surface elasticity and the destruction of the ordered structure of protein fibers at concentrations higher than 1 × 10⁻⁴ M. With the further increase in the surfactant concentration, the thread-like aggregates disappear, the packing of thin fibers becomes less tight, a uniform layer disintegrates into separate islands, and finally, the protein is displaced from the interface. Full article

(This article belongs to the Collection Feature Papers in Polymer Processing and Engineering)

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21 pages, 3960 KiB

Open AccessArticle

The Effect of Alginate/Hyaluronic Acid Proportion on Semi-Interpenetrating Hydrogel Properties for Articular Cartilage Tissue Engineering

by Izar Gorroñogoitia, Sheila Olza, Ana Alonso-Varona and Ane Miren Zaldua

Polymers 2025, 17(4), 528; https://doi.org/10.3390/polym17040528 - 18 Feb 2025

Viewed by 485

Abstract

One of the emergent regenerative treatments for the restoration of the articular cartilage is tissue engineering (TE), in which hydrogels can functionally imitate the extracellular matrix (ECM) of the native tissue and create an optimal microenvironment for the restoration of the defective tissue. [...] Read more.

One of the emergent regenerative treatments for the restoration of the articular cartilage is tissue engineering (TE), in which hydrogels can functionally imitate the extracellular matrix (ECM) of the native tissue and create an optimal microenvironment for the restoration of the defective tissue. Hyaluronic acid (HA) is known for its potential in the field of TE as a regenerative material for many tissues. It is one of the major components of the articular cartilage ECM contributing to cell proliferation and migration. HA is the only non-sulphated glycosaminoglycan (GAG). However, herein, we use a HA presenting a high amount of sulphated glycosaminoglycans (sGAGs), altering the intrinsic properties of the material particularly in terms of biological response. Alginate (Alg) is another polysaccharide widely used in TE that allows stiff and stable hydrogels to be obtained when crosslinked with CaCl₂. Taking the benefit of the favourable characteristics of each biomaterial, semi-interpenetrating (semi-IPN) hydrogels had been developed by the combination of both materials, in which alginate is gelled, and HA remains uncrosslinked within the hydrogel. Varying the concentration of alginate and HA, the final rheological, viscoelastic, and mechanical properties of the hydrogel can be tailored, always seeking a trade-off between biological and physico-mechanical properties. All developed semi-IPN hydrogels have great potential for biomedical applications. Full article

(This article belongs to the Special Issue Polysaccharide-Based Materials: Developments and Properties)

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16 pages, 5865 KiB

Open AccessArticle

Biodegradable Fiber Preparation Technique to Meet Industrial Requisites Through Sheath-Core Melt-Spinning

by Jin Yoo, Ga Hee Kim, Jun-Yeop Shim, Seok Eon Lee, Shi Hyeong Kim, Taehwan Lim and Jun Sik Son

Polymers 2025, 17(4), 527; https://doi.org/10.3390/polym17040527 - 18 Feb 2025

Viewed by 582

Abstract

Biodegradable polymers are essential for sustainable plastic life cycles and contribute to a carbon-neutral society. Here, we explore the development of biodegradable fibers with excellent mechanical properties using polypropylene (PP) and thermoplastic starch (TPS) blends. To address the inherent immiscibility between hydrophobic PP [...] Read more.

Biodegradable polymers are essential for sustainable plastic life cycles and contribute to a carbon-neutral society. Here, we explore the development of biodegradable fibers with excellent mechanical properties using polypropylene (PP) and thermoplastic starch (TPS) blends. To address the inherent immiscibility between hydrophobic PP and hydrophilic TPS, hydrophilic modification and a masterbatch approach were employed. Melt-spinning trials demonstrated that the modified PP and TPS blends (mPP/TPS) exhibited excellent spinnability and processability comparable to virgin PP. A sheath-core configuration was introduced to enhance biodegradability while maintaining structural stability, with an mPP-rich part as the core and a TPS-rich part with a biodegradable promoter (BP) as the sheath. SEM and DSC analyses confirmed strong interfacial compatibility, uniform fiber morphology, and single melting points, indicating no phase separation. Mechanical testing showed that the sheath-core fibers met industrial requirements, achieving a tenacity of up to 2.47 gf/den and tensile strain above 73%. The addition of a BP increased the biodegradability rate, with PP/TPS/BP fibers achieving 65.93% biodegradation after 115 days, compared to 37.00% for BP-free fibers. These results demonstrate the feasibility of blending petroleum-based polymers with bio-based components to create fibers that balance biodegradability, spinnability, and mechanical performance, offering a sustainable solution for industrial applications. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

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15 pages, 33478 KiB

Open AccessArticle

Representative Test Material for Validation of Density Separation as Part of Microplastic Quantification in Drinking Water

by Jessica Ponti, J. Francisco Barbosa-de-Bessa, Dora Mehn, Guillaume Bucher, Gabriella F. Schirinzi, Francesco Fumagalli and Douglas Gilliland

Polymers 2025, 17(4), 526; https://doi.org/10.3390/polym17040526 - 18 Feb 2025

Viewed by 408

Abstract

The evolving regulatory landscape for microplastics—including the European Union’s Drinking Water Directive—underscores the importance of addressing the analytics of emerging contaminants in water, ensuring public health protection, and fostering scientific advancements in environmental monitoring. This work aims to contribute to these advancements by [...] Read more.

The evolving regulatory landscape for microplastics—including the European Union’s Drinking Water Directive—underscores the importance of addressing the analytics of emerging contaminants in water, ensuring public health protection, and fostering scientific advancements in environmental monitoring. This work aims to contribute to these advancements by sharing the strategy of test material selection and characterisation for the validation of sample treatment protocols. The article describes a PVC-based representative test material of industrial origin, its physicochemical characterisation, and its application in density separation procedure evaluation, compatibly with the European Commission’s recommendations for quantifying microplastics in water for human consumption. The work shares our protocol for the durable fluorescent labelling of microplastic particles and for the centrifugal density separation of microplastics from other particulate contaminants in drinking water samples. It reports density and viscosity values for the zinc chloride solutions used to feed the theoretical calculations and recovery values achieved with the presented density separation protocol. Full article

(This article belongs to the Special Issue Micro- and Nanoplastics Engineering and Design for Research)

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20 pages, 7939 KiB

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Plastic Devolatilisation Kinetics During Isothermal High-Temperature Pyrolysis: Focus on Solid Products (Part I)

by Ieva Kiminaitė, Sebastian Wilhelm, Lukas Martetschläger, Clara Leonie Brigitte Eckert, Marcos Berenguer Casco, Nerijus Striūgas and Sebastian Fendt

Polymers 2025, 17(4), 525; https://doi.org/10.3390/polym17040525 - 18 Feb 2025

Viewed by 445

Abstract

Incineration remains Europe’s main practice for plastic packaging waste treatment, primarily due to the limitations of mechanical recycling technology. Consequently, research and development of more sustainable and flexible approaches are of high importance. Thermochemical conversion of polypropylene, polystyrene, and municipal plastic packaging mix [...] Read more.

Incineration remains Europe’s main practice for plastic packaging waste treatment, primarily due to the limitations of mechanical recycling technology. Consequently, research and development of more sustainable and flexible approaches are of high importance. Thermochemical conversion of polypropylene, polystyrene, and municipal plastic packaging mix via high-temperature flash pyrolysis (1000 °C/s) is studied in this research, focusing on the kinetics and yields of the devolatilisation stage. The primary stage results in the formation of volatile organic compounds considered intermediate products for carbon black production. The experiments were conducted in a pressurised wire mesh reactor, investigating the influence of temperature (600–1200 °C), residence time (0.5–10 s), and pressure (1–25 bar). The positive effect of temperature on the volatile yield was observed up to 2–5 s. The devolatilisation stage was completed within a maximum of 5 s at temperatures ranging from 800 to 1200 °C. The pressure was determined to be a kinetically limiting factor of the process to up to 800 °C, and the effect was not present at ≥1000 °C. Raman spectroscopy measurements revealed that pyrolytic carbon deposited on the post-experimental meshes is structurally similar to the industrially produced carbon black. The kinetic data and developed model can be further applied in the upscale reactor design. Full article

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

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16 pages, 5102 KiB

Open AccessArticle

Tröger’s Base Polyimide Membranes with Enhanced Mechanical Robustness for Gas Separation

by Xingfeng Lei, Zixiang Zhang, Yuyang Xiao, Qinyu Yu, Yewei Liu, Xiaohua Ma and Qiuyu Zhang

Polymers 2025, 17(4), 524; https://doi.org/10.3390/polym17040524 - 18 Feb 2025

Viewed by 512

Abstract

The rigid V-shaped Tröger’s base (TB) unit has been proven efficacious in creating microporosity, making TB-based polyimides (PIs) exhibiting significant advantages in simultaneously increasing gas permeability and selectivity for the separation industry. However, TB-based PIs commonly display undesired mechanical [...] Read more.

The rigid V-shaped Tröger’s base (TB) unit has been proven efficacious in creating microporosity, making TB-based polyimides (PIs) exhibiting significant advantages in simultaneously increasing gas permeability and selectivity for the separation industry. However, TB-based PIs commonly display undesired mechanical performance due to the low molecular weight resulting from the evident steric hindrance and low reactivity of TB-containing diamines. Herein, a novel diamine-containing bisimide linkage (BIDA) has been synthesized and then polymerized with paraformaldehyde via a moderate “TB polymerization” strategy to furnish polymers simultaneously, including imide linkages and TB units in the polymer main chains, namely, TB-PIs. This TB polymerization strategy avoids the direct polymerization of dianhydride with low-reactivity TB diamine. After incorporating a meta-methyl substituent into BIDA diamine, the m-MBIDA diamine-derived m-MTBPI ultimately exhibits a high molecular weight, good tensile strength (90.4 MPa) and an outstanding fracture toughness (45.1 MJ/m³). And more importantly, the m-MTBPI membrane displays an evidently enhanced gas separation ability in comparison with BIDA-derived TBPI, with overall separation properties much closer to the 1991 Robeson upper bound. Moreover, no sign of plasticization appears for the m-MTBPI membrane when separating a high-pressure CO₂/CH₄ mixture (v/v = 1/1) up to 20 bar, with the CO₂/CH₄ mixed-gas separation performance approaching the 2018 upper bound. Full article

(This article belongs to the Special Issue Advances in High-Performance Polymer Materials)

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Polymers, Volume 17, Issue 4 (February-2 2025) – 121 articles

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