Chinese Journal of Polymer Science最新文献

Strong polyelectrolyte brushes (SPBs) play an important role in enabling material surface functionalization due to their unique stimuli-responsive properties. Although the unexpected pH responsiveness of SPBs has been revealed in the past ten years, it is still unclear if the pH-responsive properties of SPBs are affected by the brush thickness. In this study, we employed the positively charged poly[2-(methacryloyloxy)ethyl] trimethylammonium chloride (PMETAC) and negatively charged sodium poly(styrenesulfonate) (NaPSS) brushes as model systems to explore the effect of thickness on the pH-responsive properties of SPBs. The results demonstrate that the pH-responsive properties of SPBs manifest different dependences on the brush thickness. Specifically, for both PMETAC and NaPSS brushes, the pH-responsive hydration and stiffness are influenced by the thickness, and the pH-responsive wettability and adhesion are almost unaffected by the thickness. This work not only provides a clear understanding of the relationship between the brush thickness and the pH responsiveness of SPBs, but also offers a new method to control the pH-responsive properties of SPBs.

Polymers often exhibit multi-state conformational transitions with multiple pathways as temperature varies. However, characterizing the inherent features of these pathways is hindered by the lack of physical characterizations that can distinguish various transition pathways between complex and disordered states. In this work, we introduced a machine-learning framework based on spatiotemporal point-cloud neural networks to identify and analyze conformational transition pathways in polymer chains. As a case study, we applied this framework to the temperature-induced unfolding of a single semi-flexible polymer chain, simulated via coarse-grained molecular dynamics. We first combined spatiotemporal point cloud neural networks and contrastive learning to extract features of conformational evolution, and then we employed unsupervised learning methods to cluster distinct transition pathways and unfolding trajectories. Our results reveal that, with increasing temperature, semi-flexible polymer chains exhibit five distinct unfolding pathways: rigid rod → random coil; small toroid → large toroid → hairpin → random coil; rod bundle → hairpin → random coil; hairpin → random coil; and tailed structure → random coil. We further calculated the structural order parameters of those typical conformations with distinct transition pathways, we distincted five transition mechanisms, including the straightening of rigid rods, tightening of small rings, expansion of hairpin ends, symmetrization of rod bundles, and retraction of tailed structures. These findings demonstrate that our framework presents a promising data-driven approach for analyzing complex conformational transitions in disordered polymers, which might be potentially extendable to other heterogeneous systems like intrinsically disordered proteins.

Anion exchange membrane water electrolysis (AEMWE) synergize the kinetic merits of alkaline systems, zero-gap configurations and compatibility with non-noble metal catalysts, offering a promising pathway toward green hydrogen production. Nevertheless, practical exploitation was hindered by critical challenges: inferior alkaline stability, insufficient mechanical integrity, and detrimental hydrogen crossover of anion exchange membranes (AEMs), which compromise both device durability and operational safety. Here, we engineered a porous expanded polytetrafluoroethylene (e-PTFE)-reinforced poly(arylene quinuclidinium) membrane that enhances AEM mechanical robustness, prevents stress-induced rupture, and suppresses hydrogen crossover during electrolyzer operation. Specifically, the reinforced poly(arylene quinuclidinium) membrane (R-PTPQui) exhibited a tensile strength of 56 MPa and an elongation at break of 55%. Moreover, it effectively reduced hydrogen permeation in the electrolyzer, achieving an extremely low H₂-to-O₂ (HTO) value of 0.44 vol% at 0.1 A·cm⁻². The R-PTPQui-based electrolyzer achieved a high current density of 4.9 A·cm⁻² at 2.0 V and a Faradaic efficiency of 98.6% using a non-precious anode catalyst. These advances significantly strength the compatibility of poly(arylene quinuclidinium)-based AEMs for industrial-scale green hydrogen generation.

Due to environmental concerns and the oil crisis, biodegradable polymer foams have garnered increasing attention. Among all biodegradable materials, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)) distinguishes itself with the advantage of being biodegradable in all natural environments. However, preparing P(HB-co-HV) foam with a fine cellular structure remains challenging. Herein, P(HB-co-HV) foams with a double melting peak structure were developed. P(HB-co-HV) samples were first heated briefly near the melting temperature to melt most of the crystals, followed by saturation and foaming at a lower temperature (foaming temperature). P(HB-co-HV) foams with cell sizes of 7.1–30.0 µm and relative densities ranging from 0.3 to 0.9 were prepared, and the foaming temperature window was as wide as 16 °C. The effect of heat treatment temperature and foaming temperature on the crystallization and cell structure was investigated through DSC and SEM. It was found that the high-melting temperature crystals generated during the saturation step significantly improved the cell structure of P(HB-co-HV), since these crystals can enhance the heterogeneous cell nucleation and hinder the cell growth during foaming. The low-melting temperature crystals were formed during foaming. In situ WAXD analysis during heating showed that the high- and low-melting peaks corresponded to HV-unit-excluded and HV-unit-included PHB crystals, respectively.

An efficient strategy has been developed to reconstruct chain folding and traversing of poly(L-lactide) (PLLA) during melt crystallization based on the selective hydrolysis of its amorphous regions. The molecular weights of the pristine PLLA (crystalline part), single stem, and single cluster were determined by gel permeation chromatography (GPC) according to their evolution during alkali hydrolysis. The maximum-folding-number (in a single cluster) and minimum-cluster-number (in one polymer chain) were obtained using these molecular weights. With the help of two numbers, the chain folding and traversing during the melt crystallization process (at 120 °C) of PLLA can be described as follows. Statistically, in a single polymer chain, there are at least 2 clusters consisting of up to 6.5 stems in each of them, while the rest of the polymer chain contributes to amorphous regions. Our results provide a new strategy for the investigation and fundamental understanding of the melt crystallization of PLLA.

A series of imido-vanadium(V) complexes bearing bidentate phenoxy-phosphine ligands were synthesized and characterized by NMR, elemental analysis, and single-crystal X-ray diffraction. These complexes demonstrated excellent catalytic performance in ethylene/1-hexene copolymerization, achieving high activities of 12.0×10⁶–49.0×10⁶ g_polymer ·(mol_V)⁻¹·h⁻¹ and affording random copolymers with tunable 1-hexene incorporations. These catalysts also exhibited ultrahigh activity, up to 112.2×10⁶ g_polymer ·(mol_V)⁻¹·h⁻¹, in ethylene/norbornene (NB) copolymerization, yielding cyclic olefin copolymers with adjustable NB incorporations. Remarkably, these catalysts demonstrated exceptional tolerance toward polar functional groups, enabling efficient copolymerization of ethylene with both 10-undecen-1-ol (U-OH) and 5-norbornene-2-methanol (NB-OH), incorporating about 2 mol% polar comonomers with high efficiency. Different with the catalytic behaviors in copolymerization of ethylene with nonpolar comonomers, the catalytic activities in E/U-OH copolymerization (25.7×10⁶ g_polymer ·(mol_V)⁻¹·h⁻¹) were much higher than those in E/NB-OH copolymerization (8.6×10⁶ g_polymer ·(mol_V)⁻¹·h⁻¹). DFT calculations revealed that the catalytic performance is governed by synergistic electronic and steric effects. For E/NB copolymerization, strong preference for cyclic olefins was attributed to favorable transition state stabilization. In polar comonomer systems, steric effects were predominant, with NB-OH exhibiting a larger buried volume around vanadium center upon coordination compared to U-OH. Overall, this work provides fundamental insights into vanadium-catalyzed (co)polymerization and offers new strategies for tailored polyolefin design.

Polycaprolactam (PA6) is an important engineering plastic known for its excellent strength and processability, making it widely applicable in the automotive and transportation industries. Previous studies have demonstrated that incorporating a small amount of organic-modified montmorillonite (OMMT) can significantly enhance the gas barrier properties of PA6. Based on PA6/OMMT, this study further introduced maleic anhydride-grafted ethylene-octyl copolymer (mPOE) and polytetrafluoroethylene (PTFE). Morphological characterization revealed the successful manipulation of the microstructure within this toughening system, revealing a distinctive tassel bundle morphology in the ternary blend of PA6/mPOE/PTFE. in the quaternary PA6/OMMT/mPOE/PTFE system, scanning electron microscopy (SEM) analysis demonstrated that the special “tassel bundle (TB)” morphology could induce an ordered arrangement of OMMT nanosheets, leading to synergistic improvements in both toughness and gas barrier performance. These findings offer promising potential for applications requiring simultaneously high gas barrier properties and enhanced toughness, particularly in hydrogen storage tanks and related industrial fields.

Knots are discovered in a wide range of systems, from DNA and proteins to catheters and umbilical cords, and have thus attracted much attention from physicists and biophysicists. Langevin dynamics simulations were performed to study the knotting properties of coarsegrained knotted circular semiflexible polyelectrolyte (PE) in solutions of different concentrations of trivalent salt. We find that the length and position of the knotted region can be controlled by tuning the bending rigidity b of the PE and the salt concentration C_S. We find that the knot length varies nonmonotonically with b in the presence of salt, and the knot localizes and is the tightest at b=5. As b>5, the knot swells with b increase. In addition, similar modulations of the knot size and position can be achieved by varying the salt concentration C_S. The knot length varies nonmonotonically with C_S for b>0. The knot localizes and becomes tightest at C_S=1.5×10⁻⁴ mol/L in the range of C_S≤1.5×10⁻⁴ mol/L. As C_S>1.5×10⁻⁴ mol/L, the knot of the circular semiflexible PE swells at the expense of the overall size of the PE. Our results lay the foundation for achieving broader and more precise external adjustability of knotted PE size and knot length.

Poly(vinyl alcohol) (PVA) hydrogels have garnered significant attention for tissue engineering, wound dressing, and electronic skin sensing applications. However, their poor mechanical performance severely restricts their multifunctional application in many scenarios. To address this limitation, PVA/tannic acid (TA)@carbon nanotubes (PVA/TA@CNTs) composite hydrogels with triple crosslinking networks were prepared through freezing-thawing and the solvent-induced shrinkage method, utilizing tannic acid-carbon nanotubes (TA@CNTs) as reinforcing units and a Ca²⁺ crosslinking strategy. The enhanced interfacial networks consisting of PVA crystalline domains, hydrogen bonding, and metal co-ordination endowed the composite hydrogel with a high mechanical strength, excellent flexibility, and fracture toughness, accompanied by a significant increase in crystallinity. The tensile strength and fracture toughness of the composite hydrogel reached up to about 7.0 MPa and 17.0 MJ/m³, which were roughly 8 and 10 times higher than neat PVA hydrogel, respectively. The composite hydrogel demonstrated good cytocompatibility, significantly addressing the challenge of balancing structural reinforcement with biosafety in hydrogels. This methodology establishes a rational design for fabricating mechanically robust yet tough PVA hydrogels for biomedical applications.

Effective antifouling coatings are critical for protecting marine infrastructure from biofouling and environmental degradation; however, achieving long-term antifouling performance along with environmental stability remains a major challenge. In this study, a multifunctional bio-based epoxy coating is developed by integrating a dual-action antifouling system. Cinnamic acid (CA), which is known for its antibacterial and UV-shielding properties, was chemically grafted into ethylene glycol diglycidyl ether (EGDE) to provide intrinsic antifouling and anti-UV functions. Simultaneously, the KH560-modified silica aerogel was incorporated to create a dense hydrophobic surface that repels microorganism adhesion. The resulting coating exhibited a superhydrophobic contact angle of 154.3°, an ultralow surface energy, and exceptional resistance to protein and algal adhesion. Additionally, it achieves 99% bactericidal efficiency against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) while maintaining high transparency and ease of processing. These results highlight a promising strategy for designing durable and ecofriendly antifouling coatings suitable for demanding marine environments.