Journal of Polymer Research最新文献

Metal oxide nanoparticle-polymer hybrids are appealing solid materials that combine enhanced chemical and physical characteristics with elasticity, making them highly suitable for electrical device applications. This study focuses on the preparation and characterization of hybrid films composed of carboxymethyl cellulose (CMC) and polyethylene oxide (PEO) in a 70:30 weight ratio, incorporated with zinc oxide and copper oxide nanoparticles (ZCNP). The films were fabricated using a solution casting method, with the nanoparticles synthesized via the sol-gel technique. The temperature dependence of key electrical properties, including dielectric constant (ε'), dielectric modulus, relaxation behavior, AC conductivity, and activation energy, was systematically analyzed. At frequency (f) = 10 Hz, ε' of the CMC/PEO and CMC/PEO-ZCNP (2 wt%) samples was 56.34 and 7916.36 at 308 K respectively, while it reached 6222.65 and 152364 when the temperature changes to 333 K. Their relaxation time (τ) dropped from 59.5 and 0.40 µs to 1 and 0.18 µs in the same temperature range. At f = 10 Hz and T=308 K, electrical conductivity (σ') improved, with CMC/PEO showing log(σ') = -9.3605 (σ' = 4.36E-10 Ω·m⁻¹) and 2% ZCNP achieving log(σ') = -7.3142 (σ' = 4.85E-8 Ω·m⁻¹). The results demonstrated a significant enhancement in the dielectric constant of the hybrid films compared to the unmodified polymer blend, while maintaining a low dielectric loss. These enhancements are attributed to the incorporation of zinc oxide and copper oxide nanoparticles, which promote multiple polarization mechanisms and enhance charge carrier dynamics. The findings suggest that these hybrid films hold great potential for use in high-density energy storage devices and integrated thin-film capacitors, offering a scalable and efficient solution for next-generation electronic applications.

Polystyrene, when present as microplastics, is a significant pollutant with detrimental effects on human health. In light of this issue, our study introduces a method for the degradation of polystyrene through photocatalysis and its subsequent removal from drinking water via filtration. We investigated the photocatalytic degradation of 500 nm polystyrene (PS) using the highly efficient In₂O₃-rGO nanocomposite under visible light. FESEM analysis demonstrated that, after 12 h of visible light exposure, the size of the polystyrene beads decreased from 500 to 280 nm. This process resulted in a 56% degradation efficiency of polystyrene by the In₂O₃-rGO nanocomposite. Furthermore, the degraded polystyrene beads began to form networks, and with continued exposure to visible light, they merged into larger aggregates, as observed in FESEM images. Raman spectroscopy showed an increase in the peak at 1003.20 cm⁻¹ with extended visible light exposure, indicating a crucial step in the degradation process. Additionally, FTIR analysis confirmed the formation of carbonyl groups with increased light exposure, supporting the degradation of polystyrene. Our study presents a method and mechanism demonstrating how the In₂O₃-rGO nanocomposite not only reduces the size of polystyrene but also facilitates the formation of networks among degraded polystyrene beads, aiding in the filtration of smaller polystyrene particles.

In this work, free radical solution polymerization was used to prepare polymeric nanocomposite films by copolymerization of flexible butyl acrylate (BA) monomer and modified nano−silica with methyl acrylate (MMA) monomer. Our findings showed that the addition of BA monomer and nano−silica had limited effect on the transmittance of PMMA films, and the transmittance could achieve as high as 93%. Perfect overall properties of the as−prepared films (with a tensile strength of 36 MPa and an elongation at break of 42%) could be achieved when the monomer MMA:BA was set as 6:2 at a nano−silica content of 20 wt%. The PMMA−based nanocomposite films prepared in this work possessed excellent transparency, desired toughness and good hydrophobicity, which made them potentially promising for the applications as protective films for polarizing films.

The integration of two-dimensional materials into polymer matrices has garnered significant attention in recent years owing to their potential to enhance the mechanical and electrical properties of composite materials. This study focuses on synthesizing polyvinyl alcohol (PVA) and Ti₃C₂T_x MXene into a nonwoven nanofiber (NF) composite mat using electrospinning. Following the electrospinning process, the fibers underwent pyrolysis, which is a crucial step that enhances their electrical conductivity and structural integrity. To characterize the nanofibers, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and field-emission scanning electron microscopy (SEM) were performed. XRD and FTIR analyses confirmed the presence of both PVA and MXene, whereas SEM revealed improved morphological properties, including an increased surface area and a higher number of active sites. The Raman spectra provided insights into the defect densities, with the I_D/I_G ratio indicating that the incorporation of MXene and subsequent pyrolysis effectively increased the defect density in PVA while enhancing its amorphous nature. Importantly, electrical conductivity measurements demonstrated a substantial enhancement in the direct current conductivity of the pyrolyzed PVA-MXene composite fibers.

Polylactic acid (PLA) and poly(butylene succinate) (PBS) are thermodynamically incompatible systems, and usually require the addition of compatibilizers or chain extenders to improve their compatibility. In this paper, PBS grafted itaconic anhydride (IAH) (PBS-g-IAH) was prepared by melt grafting method with diisopropylbenzene peroxide (DCP) as initiator and was used as the compatibilizer to prepare PLA/PBS-g-IAH/PBS composite. FTIR and Raman spectroscopy were used to characterize the grafting products. The effects of the dosages of DCP and IAH on the grafting rate of PBS-g-IAH were investigated. The results of FTIR and Raman spectroscopy showed that IAH had been successfully grafted onto the PBS molecular chains. When the amounts of DCP and IAH were 0.4% and 10% of the PBS mass, respectively, the product achieved the highest grafting rate of 1.46%. The crystallization properties, micro-morphology, rheological properties, mechanical properties, and heat resistance of the composites were investigated by DSC, SEM, rotary rheometer, electronic tensile testing machine, impact testing machine and Vicat softening temperature tester. The results showed that as the grafting rate of PBS-g-IAH was 1.30% and the mass fraction was 5%, the composite exhibited the best comprehensive properties, and the elongation at break was increased from 235.5% to 381.4% compared with that without PBS-g-IAH. The impact strength was increased from 4.4 kJ/m² to 5.9 kJ/m² and the softening temperature was increased from 72.5℃ to 129.4℃. According to the DSC analysis, the T_g of PLA/PBS blends decreased from 54.4℃ to 46.7℃ when the mass fraction of PBS-g-IAH was 5%. The SEM images showed that PBS-g-IAH had a good compatibilizing effect on PLA/PBS blend.

To develop next-generation polyacrylonitrile (PAN) based carbon fibers with enhanced mechanical performance, it is crucial to understand the plastic deformation mechanisms of PAN fibers during stretching process. In this work, the morphological changes of intermediate microfibril structures within PAN fibers at various stages along the stress–strain process were visualized using the ultrathin sectioning technology and electron microscopy. Upon approaching the yield point, the crystalline structure's constraints were compromised, leading to the initiation of microfibril slippage. During the necking process, the varying mechanical responses of the interpenetrated network resulted in a radial gradient in the orientation degree and packing density of microfibrils along the stretching direction. The stretching-induced fibrillation resulted in the alignment of microfibril elements and subsequent recrystallization, thereby facilitating significant macroscopic deformation. The fracture failure of PAN fibers was attributed to the cracking and breakage of the microfibril network, which involved the pull-out of microfibril elements and disentanglement of the interpenetrated network. Furthermore, a novel structural model was developed to elucidate the plastic deformation mechanisms of microfibril elements during macro-drawing of fibers. This model is anticipated to enhance the design and optimization of the microstructure and processing techniques for high-performance PAN fibers.

Research on the fabrication of polymeric membranes for energy conversion, wastewater treatment, filtration, and gas separation applications has attracted attention for high-temperature and chemical-resistant polymeric materials such as poly ether ether ketone (PEEK). In this study, a non-solvent induced phase separation (NIPS) technique was introduced to prepare a porous PEEK membrane. 4-chlorophenol (4 CP) was used as a compatible solvent for the dissolution and precipitation of PEEK, which was achieved through solidification of the membrane by NIPS in three different nonsolvents: ethanol (EtOH), water, and isopropanol (IPA). The processing of PEEK in 4 CP had no effect on its chemical structure, and the achieved thermal properties were similar to virgin PEEK. Process parameters such as polymer concentration and the use of nonsolvents were studied to understand their effects on membrane morphology and performance. Changes in polymer concentration not only alter the casting solution rheology but also restrict the percentage of polymer, which affects the membrane morphology, whereas the use of nonsolvents affects the morphology through diffusion of solvent into nonsolvent. EtOH and IPA as nonsolvents showed sudden changes in the color of the membrane from transparent to white, which resulted in instantaneous de-mixing of solvent and nonsolvent, that formed finger-like structure at 7 wt% and 9 wt% polymer concentrations. Water as a nonsolvent showed a slow color change for phase separation, which resulted in delayed de-mixing, and formed sponge-like structure in the membranes with 7 wt%, 9 wt%, and 11 wt % polymer concentrations. Partial solidification before immersion of the membrane in nonsolvents was observed at 11 wt% polymer concentration owing to reduction in temperature. A dense PEEK membrane was observed after 9 wt% immersion in water, and a porous PEEK membrane was observed after 11 wt% immersion in IPA. Raising the polymer concentration increased the density and reduced membrane shrinkage. The proposed novel approach advances the fabrication of PEEK membranes through the dissolution of PEEK in 4 CP without the use of concentrated acids as well as the synthesis of the PEEK precursor and NIPS process.

Due to temperature sensitivity, biocompatibility, biomedical applications and versatility a lot of interest has always been focused on the synthesis, characterization, and application of thermo-responsive hydrogels. In this study, a set of thermal responsive biocomposite hydrogels composed of poly (vinyl alcohol) (PVA) and Xanthan Gum (XG) biopolymers were fabricated by a low-cost and simple approach based on solution mixing method followed by double physical crosslinking with glycerol (Gly) and then freeze-thawing method. The obtained hydrogels have shown mechanical properties and chemical stability. SEM results demonstrated that the resultant hydrogels had asymmetric structures with interconnected non-uniform porous networks offering sufficient space for cell growth, attachment, proliferation, and drug or water molecule absorption and release. Drug-loaded hydrogels through the swelling diffusion method display good absorption and distribution of drug (N atoms) which were confirmed by EDX. The presence of all components in prepared hydrogels was approved by FT-IR and XRD analysis. The obtained samples also showed suitable mechanical and thermal stability. Moreover, UV–Vis spectroscopy was employed to assess the drug release profile of metronidazole from the hydrogels at various pH and temperatures, revealing a temperature-dependent and slow-release pattern of metronidazole over 10 h. Therefore, they are a potential candidate for controlled drug delivery applications. The antimicrobial properties of the hydrogels were investigated against Escherichia coli and Bacteroides fragilis. The results indicated they are only effective against Bacteroides fragilis without any growth inhibition against Escherichia coli, PVA-Gly-XG hydrogel is a promising candidate worthy of extensive exploration in specific anti-bacterial systems.

The aim of this paper is to present a 1D thermodynamic model describing the rise in temperature induced by self-heating phenomenon occurring in cyclic solicitations of polymers and reinforced thermoplastics. The proposed model was validated for a neat Polyamide 6.6 (PA6.6) for various frequencies and water absorption configurations. This work showed that the presence of water molecules in the network cannot be the only explanation for the observed rise in temperature of the studied aged PA6.6. A physical explanation of this exacerbated rise in temperature is then proposed by modelling the unrecoverable molecular-chain network reorganisation and damage, generally known as the “plasticising” effect of water.

The copolymerization of ethylene and 1-butene in the presence of hydrogen using a dual-site metallocene catalyst was optimized to produce copolymers with pre-designed bimodal molecular weight distributions (MWDs). This optimization employed artificial neural networks (ANNs) featuring both forward and inverse models. A rigorous training phase was conducted for the ANN models using a dataset derived from Monte Carlo simulations, followed by validation and testing procedures. The forward model accurately predicted bimodal distributions obtained through the Monte Carlo method based on initial copolymerization conditions, which included concentration ratios of ethylene to 1-butene and ethylene to hydrogen, while keeping co-catalyst concentration and copolymerization temperature constant. High alignment between predicted and simulated MWD was confirmed through weight fraction comparisons across multiple concentration ratios. Additionally, the inverse model effectively estimated initial copolymerization conditions using weight fraction data for specific chain lengths from bimodal MWD diagrams. As a result, the initial copolymerization conditions in the Monte Carlo simulations were successfully optimized through the integration of ANNs, leading to the generation of pre-designed bimodal distributions. The results demonstrated that HDPE synthesized under different conditions exhibited distinct properties: Case (1) produced higher crystallinity and density with lower comonomer incorporation, while Case (3) resulted in higher molecular weight but lower crystallinity. Case (2) displayed intermediate properties, resembling a bimodal distribution with similar peak heights. This study highlighted the efficacy of integrating Monte Carlo and ANN techniques for precise control over MWD, providing a robust framework for tailoring HDPE properties to enhance performance across diverse applications.