Chinese Journal of Polymer Science最新文献

The development of high-performance transparent substrates is critical for next-generation flexible electronic devices. Herein, we designed two novel meta-substituted diamines incorporating trifluoromethyl (—CF₃) and methyl (—CH₃) groups to synthesize colorless copolyimide (CPI) films via copolymerization with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)/3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). The combination of meta-substituted architecture and substituents enables the simultaneous attainment of an ultralow dielectric constant (D_k) and high transparency. The meta-substitution geometry and electronic effects of —CF₃/—CH₃ effectively suppressed charge-transfer complex (CTC) formation, expanded fractional free volume (FFV), and restricted π-electron conjugation, as validated by DFT calculations and wide-angle X-ray diffraction (WAXD) analysis. The optimized CPI film (PIA₁-6FDA/BPDA(10/0)) achieved outstanding transmittance (T₄₅₀=88.15%), ultralow dielectric constant (D_k=2.08 at 1 kHz), and minimal dielectric loss (D_f=0.0012), while maintaining robust thermal stability (T_d5%>523 °C) and mechanical strength (σ = 87.5 MPa). This work establishes a molecular engineering strategy to concurrently enhance the optical and dielectric properties, positioning meta-substituted CPIs as promising candidates for transparent flexible devices.

Quantifying the hydrogen bond (H-bond) strength of polymers is essential for rational design of advanced materials. However, direct measurement remains challenging because of the structural complexity of polymers and the weak nature of H-bonds. Vacuum-based single-molecule force spectroscopy (Vac-SMFS) offers a new and precise approach for such measurements. Using polyallylamine (PAAm) as a model polymer, the intrinsic strength (i.e., strength without external influences) of representative N—H⋯N H-bonds was quantified to be about 5.25 kJ·mol⁻¹. Comparative Vac-SMFS analysis across different polymer systems revealed that the N —H⋯N H-bonds in PAAm are unexpectedly stronger than the N—H⋯O H-bonds in poly(N-isopropylacrylamide) (PNIPAM) and the O—H⋯O H-bonds in poly(hydroxyethyl methacrylate) (PHEMA). This trend contrasts with that of established small-molecule systems. These results highlight how side-chain length and spatial configuration dictate polymer H-bond strengths, expanding the fundamental knowledge of polymer interactions and enabling the rational design of next-generation functional materials.

Carbon-fiber-reinforced plastics (CFRP) with improved mechanical properties based on modified epoxy binders were investigated in this study. By adding 15 parts by weight (p.b.w.) of copolymer of polysulfone with cardo phthalide group (PSFP-70C) to the epoxyanhydride binder, the flexural strength of the epoxy polymer was increased by 60%, the CFRP based on it by 57%, the flexural modulus of the epoxy polymer was increased by 83%, and the composite by 96%. The adhesion strength of the binder to carbon fiber reached a high level at 10 p.b.w. of thermoplastic modifier and increased by 65% compared to the unmodified binder. Scanning electron microscopy (SEM) was used to determine that in epoxyanhydride systems with a polysulfone content of 5–15 p.b.w., the structure belongs to the “matrix dispersion” type and with a content of 20 p.b.w. to the “interpenetrating phase” type. A heterogeneous structure was also observed using dynamic mechanical analysis.

The chemical structure of polyamide 6 (PA6) dictates that only 50% of hydrogen bonds participate in crystallization during the crystallization process, resulting in the properties of its products being significantly dependent on the molding process. Therefore, the design and development of nucleating agents suitable for PA6 holds great practical significance for high-performance PA6 materials. Amide-based nucleating agents can effectively improve the crystallization rate by increasing intermolecular hydrogen bond density. Further introduction of hydroxyl groups can enhance the hydrogen bonding interactions between the nucleating agent and PA6. In this study, a hydroxyl-containing amide-based nucleating agent, BHT, was designed and synthesized using a tyramine-based biomass as the raw material. These results demonstrated that BHT exhibited good structural compatibility with PA6. After adding 1 wt% BHT, the crystallization temperature of PA6 increased from 170.9 °C to 193.3 °C, the crystallinity increased 16.6%, the heat distortion temperature and Vicat softening temperature rose to 89.5 and 187.8 °C, respectively, the haze decreased to 46%, achieving the synergistic optimization of mechanical, thermal, and optical properties. The in situ time-resolved FTIR results indicated that the addition of BHT increased the enthalpy of hydrogen bond formation during the nucleation stage, facilitated the segmental conformation adjustment of PA6, and enhanced the molar concentration of trans-conformations, ultimately leading to an improvement in the crystallization rate.

Vitrimers belong to a class of polymeric materials capable of bond exchange reactions, showing great promise for environmental protection and sustainable development. However, studies on the coupling mechanism between the bond exchange kinetics and segmental dynamics near the glass transition temperature (T_g) remain scarce. Herein, we employed molecular dynamics simulations to investigate the dynamic heterogeneity of the segment motion and bond exchange in vitrimers. The simulation results revealed that the bond exchange energy barrier exerts a much stronger influence on the bond exchange kinetics than on the segmental dynamics. At lower temperatures, slower segmental relaxation further constraind the bond exchange rate. Additionally, increasing the bond exchange energy barrier markedly enhanced the dynamic heterogeneity of segment motion. A close correlation was observed between heterogeneity and bond exchange. This study elucidated the coupling mechanism between bond exchange and segmental dynamics at the molecular scale, thereby providing a theoretical basis for designing vitrimer materials with tunable dynamic properties.

Smart pesticide delivery systems based on stimuli-responsive nanocarriers have attracted considerable attention because of their potential to enhance pesticide efficiency while reducing environmental risks. In this study, a novel pH/glutathione dual-responsive pesticide delivery system was constructed through the synthesis of disulfide-bridged hollow mesoporous organosilica nanospheres (HMONs) via the Stöber method, followed by poly(acrylic acid) (PAA) coating through distillation-precipitation polymerization to form HMONs@PAA nanocomposites. The resulting abamectin-loaded system (Abamectin-HMONs@PAA) demonstrated a 12.73% pesticide loading capacity and significantly improved photostability, retaining twice as much active ingredient as free abamectin after 250 h of UV irradiation (36 W). Release studies revealed pH- and glutathione-dependent characteristics, with cumulative releases in acidic conditions exceeding those in neutral and alkaline environments by 18.66% and 40.98%, respectively, and a 14.2% increase in glutathione-containing solution (0.2 mmol·L⁻¹ in 70% ethanol) after 97 h. Bioassays showed superior performance against Plutella xylostella, with a 13.33% reduction in survival rate compared to conventional suspension at equivalent dosage (40 mg·L⁻¹), while maintaining efficacy after extensive rainfall simulation (20 events over 10 days). This study provides a promising approach for developing environmentally responsive nanopesticides with enhanced durability and controlled-release properties, offering significant potential for sustainable crop protection.

To address the poor mechanical performance and improve the tribological properties of self-lubricating polyphenylene sulfide/irradiation treated polytetrafluoroethylene (PPS/i-PTFE) blends, different aspect ratio carbon fibers (i.e., PSCF: 50, SCF: about 429) were introduced as reinforcement fillers. The results showed that the hybriding of PSCF and SCF at certain mass ratios exhibited simultaneous enhancement of mechanical and tribological performance for PPS/i-PTFE blend through the construction of synergistic lubrication and mechanical interlocking network. Specifically, the flexural strength and modulus of PPS/i-PTFE were increased by 125.6% and 389.3%, the friction coefficient and specific wear rate were decreased by 13.9% and 95%, respectively. It was worth noting that PPS composites possessed excellent integrated performance which were able to withstand sliding action under high PV (≥10 MPa·m/s) conditions, as assessed by a customized pin-on-disc tester. This work demonstrated that the formation of intact lubricating film combined with the enhanced thermal and mechanical properties were favorable for improving the tribological properties of PPS-based composites, which makes them suitable for advanced engineering applications.

UHMWPE fibers exhibit impressive modulus and strength, but they have not reached their theoretical limits. Researchers focus on molecular weight, orientation, and crystallinity of UHMWPE, yet their contributions to mechanical properties are unclear. Molecular dynamics simulations are valuable but often limited by computational constraints. Our aim is to simulate higher molecular weights to better represent real UHMWPE fibers. We used Packmol and Polyply methodologies to construct PE systems, with Polyply reproducing more reasonable properties of UHMWPE fibers. Additionally, tensile simulations showed that orientation and crystallinity greatly impact Young’s modulus more than molecular weight. Energy decomposition indicated that higher molecular weights lead to covalent bonds that can withstand more energy during stretching, thus increasing breaking strength. Combining simulations with machine learning, we found that orientation has the most significant impact on Young’s modulus, contributing 60%, and molecular weight plays the most crucial role in determining the breaking strength, accounting for 65%. This study provides a theoretical basis and guidelines for enhancing UHMWPE’s modulus and strength.

Ultra-high molecular weight polyethylene (UHMWPE) is a key material for marine applications owing to its outstanding self-lubrication and corrosion resistance. However, its long-term performance is compromised by plastic deformation in seawater. In this study, we performed a comparative analysis of the UHMWPE dynamics under seawater and water conditions to investigate the plastic deformation of UHMWPE induced by seawater. The results show that the plastic deformation of UHMWPE is amplified in seawater relative to the water conditions. Under thin fluid conditions, frictional interfaces exhibit a higher interfacial friction force and interaction energy in seawater than in water. Compared to freely diffused water molecules, hydrated ions occupy larger interchain spaces within polyethylene. Furthermore, the diffusion of hydrated ions weakens the interchain interactions, promoting more severe polyethylene chain rearrangement and accelerating seawater-induced plastic deformation in UHMWPE during friction. Furthermore, the diffused seawater accelerated the disentangling of the polyethylene chains and enhanced the orderly orientation distribution of polyethylene. Compared to free water molecules, the water molecules of hydrated ions exhibit enhanced attraction to free-flowing water molecules, thereby accelerating seawater flow across submerged UHMWPE surfaces. This flow enhancement promotes surface polyethylene chain mobility in seawater.

Functionally graded cellular structures (FGCSs) have a multitude of applications to a wide range of industries. Utilising the ever-progressing technology of additive manufacturing (AM), FGCSs can be applied to control material grading and achieve the desired mechanical properties. The current study explores the design and optimisation of FGCSs for AM, with a focus on improving the compression and impact performance of below knee (BK) prosthetic limbs made of thermoplastic polyurethane (TPU). A multiscale research methodology integrating topology optimization (TO), finite element analysis (FEA), and design of experiments (DoE) was adopted to optimise lattice structures in terms of stiffness and lightweight properties. Two-unit cell designs were considered in the study: Schwarz P gyroid and body-centered cubic (BCC). Response surface methodology (RSM) was implemented to analyse the effect of minimum and maximum cell wall thickness, cell size, and unit cell type on the mechanical performance of TPU FGCS structures. The results indicated that a Schwarz P FGCS structure with cell size, minimum and maximum cell wall thickness of 6, 0.9 and 2.8 mm, respectively, could be optimal for a compromise between performance and weight. In this optimized case, stiffness and volume fraction values of 684 N/mm and 0.64 were obtained, respectively. The study also presents a proof-of-concept design for a BK prosthetic damper, highlighting the potential of FGCSs to enhance patient comfort, reduce manufacturing costs, and enable personalised designs through 3D scanning and AM. The obtained results could be a step forward towards the incorporation of AM technologies in prosthetics, offering a pathway to lightweight, cost-effective, and functionally tailored solutions.