Journal of Polymer Science最新文献

The cover image is based on the Article Sintering evolution monitoring of ultra-highmolecular-weight polyethylene by Ying Zhou et al., https://doi.org/10.1002/pol.20230156. The cover image by Ying Zhou shows a density evolution analysis utilized to monitor the volume change during the sintering process of UHMWPE nascent powder. The analysis reveals substantial densification of the powder under pressure during heating, followed by notable density drops known as the melt explosion phenomenon. Subsequent crystallization leads to the formation of a contiguous solid UHMWPE structure within a relatively short timeframe and at moderate temperatures.

Polycondensation and ring-formation reactions are the main factors that cause instability in the molecular structure of commercial polyamide 6 (PA6) during melting. In this study, the mechanisms and interactions of the ring-formation and polycondensation reactions induced by various factors were thoroughly investigated. The findings suggest that the average molecular weight of PA6 increased by 20.4% during melting. The total monomer and oligomer content increased by 79.2%, and the ring-forming reaction was promoted with an increase in temperature. Moreover, a high concentration of the end-amino in PA6 promoted the ring-forming reaction, whereas similar concentrations of the end-amino and end-carboxyl groups were more conducive to the polycondensation reaction. In short, the nitrogen atoms in the end-amino group on the PA6 molecular chain attack the carbonyl carbon at different sites, including the carbonyl carbon in the amide bond and the carbonyl carbon in the end-carboxyl group, which is the key to the strength of the ring-formation and polycondensation reactions.

Molecular dynamics (MD) simulations are employed to assess the effects of diverse carbon nanomaterials on the thermo-oxidative aging properties and tribological behavior of perfluoroelastomer (FFKM) in high-temperature environments. In this study, carbon nanofillers such as graphene nanosheets (GNS), carbon nanotubes (CNTs), hydroxyl-functionalized graphene (OH-GNS), and hydroxyl-functionalized carbon nanotubes (OH-CNTs) are examined. The aging properties of composite systems are characterized by parameters like cohesive energy density and mean square displacement. The constant strain method is utilized to estimate the shear modulus and bulk modulus. Three-layer friction structures are established to analyze the mechanism of fillers on the tribological behavior of composites by applying shear loads. According to the MD simulation results, the addition of carbon nanofillers enhances FFKM's thermo-oxidative aging performance at 533 K, increases its bulk and shear moduli, and reduces the coefficient of friction and abrasion rate of each composite at high temperatures. Among the four nanofillers, OH-CNTs is the most effective in terms of improving FFKM performance. Stronger dipoledipole interactions and hydrogen bonding are introduced into the system by OH-CNTs, which improves the stability of the filler-matrix interface and produces stronger interfacial interactions. This work offers theoretical predictions for the design and optimization of carbon nanomaterial and FFKM polymer composites.

Understanding the doping mechanism between the dopants and the conjugated polymers (CPs) is crucial for efficiently utilizing the doping process in a controllable manner. In this work, we doped the poly(3-hexylthiophene) (P3HT) films with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) from a chlorobenzene/acetonitrile (CB/AN) solvent blend and pure AN solvent by using the common sequential doping method. We found that the dissolution ability of the dopant solvent to P3HT and the concentration of the dopant solution were two critical factors to determine the doping process (solution doping or sequential doping) and the doping region (the amorphous or the crystalline phase). When the concentration of the dopant solution was low, solution doping was dominant in the P3HT film doped with F4TCNQ CB/AN solution, and the amorphous regions were doped in the P3HT film doped with F4TCNQ AN solution. With the increase of the dopant solution concentration, the ratio of ordered integer charge transfer (ICT) species, which formed from sequentially doped crystalline domains in the P3HT precast film, increased. Based on the above doping mechanism, a P3HT film with good electrical and tensile performance could be constructed by doping from F4TCNQ CB/AN solution with a relatively low concentration. Our work indicates that the dissolution or swelling ability of the dopant solvent to CP is an important factor in determining not only the doping mechanism but also the electrical and mechanical performances of doped CP films.

In recent years, the prevalence of bone diseases is showing an increasing trend, which is mainly attributed to the aging of the global population. However, bone repair and regeneration are still an unsolved problem in the treatment of bone diseases, which include a series of biological events. Photocrosslinked natural hydrogel-based microspheres (PNHMs) are spherical particles composed of photocrosslinked natural hydrogel components. Due to their morphology, injectability, and biocompatibility, PNHMs are widely used in tissue regeneration, particularly for bone defects. In this article, we review the available photocrosslinked natural materials for PNHMs, and then introduce their preparation methods. After that, we summarize the important advanced functionalities of PNHMs. For example, PNHMs can be loaded with different active ingredients to exert anti-inflammatory, antibacterial, and antioxidant effects, while also realizing lubrication due to their specific shape and size distribution. In addition, the function of capturing ions can be realized via coordination. When applied in bone tissue engineering, PNHMs can promote angiogenesis and osteogenesis, with great potential in the treatment of bone diseases. Finally, the challenges and prospects of PNHMs for bone repair are discussed.

Storing CO₂ and converting it into valuable substances are crucial for addressing climate change. While poly(propylene carbonate) (PPC), formed through the copolymerization of CO₂ and propylene oxide, holds promise in commercial applications, practical limitations arise due to inherent property constraints. Additionally, the lack of systematic research on PPC biodegradation complicates its post-use disposal. In this study, we synthesized various polymers, including PPC homopolymers, PPC/castor oil star copolymers, and PPC/poly(l-lactic acid) multiblock copolymers (PPC-mb-PLLAs), not only to mitigate the brittle properties of PPC but also to systematically explore their biodegradability. Both natural soil and industrial composting conditions were employed to assess the biodegradation of the polymers. Furthermore, metagenomic analysis identified the microorganisms responsible for polymer degradation, offering valuable insights into the mechanism of the biodegradation process.

Hydrogel flexible sensors are gaining significant interest due to their distinct biocompatibility, flexibility, and unique features of being adjustable and injectable, but there are still problems of poor self-healing performance and low conductivity in the current stage of research. In this work, a prefabricated blending method was used to construct a dual-network system using polyacrylamide (PAM), carboxymethyl chitosan (CMCS), and tannin acid (TA), and ferric ions (Fe³⁺) were introduced to apply ionically conductive organic hydrogels to flexible sensors. The PAM/CMCS-Fe³⁺/TA hydrogels have good fatigue resistance and self-healing properties, and their conductivity is as high as 6.42 S/m. This hydrogel-based sensor for strain sensing purpose offers a lot of promise for flexible sensor applications since it can provide steady, dependable, and repeatable electrical impulses.

Piezoelectric energy harvesters (PEHs) developed from electrospun polyvinylidene fluoride (PVDF) fibers offer flexibility and superior piezoelectric output, making them promising for self-powered systems and sensors. Nonetheless, the electromechanical conversion efficiency of conventional electrospun PVDF fibers is impeded by their limited pressure-strain range. Herein, elastic porous PVDF microspheres are introduced in-situ via electrospinning to craft a piezoelectric membrane with higher compressive strain. The PVDF microspheres are uniformly embedded between the fibers in a sandwich fashion, and their dimension is easily tunable by varying spinning solution's concentration. Moreover, the micropores on the PVDF microspheres created by removing pre-mixed SiO₂ template not only elevates the β crystal content of PVDF to 82.19%, but also improves the compressibility, significantly boosting the piezoelectric output. The microsphere alloyed PVDF PEH delivers a piezoelectric output of 33.0 V and a power density of 8 μW/cm², over 5.8 times that of conventional electrospun PVDF membrane, and can consistently charge lithium-ion batteries. Our research unveils a novel strategic path to modify fiber structured PEHs, advancing their applications in self-powered systems.

Smart microgels can be used as sorbents, possessing high surface area and rapid stimuli-responsiveness. A series of poly(N-isopropylacrylamide) (pNIPAM) and pNIPAM-co-starch nanoparticles (pNIPAM-co-SNPs) thermo-responsive microgels were synthesized, presenting different hydrophilic/hydrophobic behavior according to the composition. The adsorption studies were carried out for methylparaben (MPB), ethylparaben (EPB), propylparaben (PPB), butylparaben (BPB), and bisphenol A (BPA), and the extraction and desorption efficiency were determined by high-performance liquid chromatography and spectrophotometric detection (HPLC-UV). The effect of microgel phase transition according to the temperature and the copolymerization with SNPs in each sorptive step was investigated. The extraction of less polar compounds (BPA, PPB, and BPB) above the volume phase transition temperature (VPTT) was favored, driven by a predominant hydrophobic interaction. According to microgel composition, the desorption capacity as a function of temperature can be influenced by hydrophilic interactions and water competition. Molecular dynamics (MD) simulations and binding free energy calculations were performed to provide theoretical evidence about binding energies between pNIPAM and BPA, which experimentally showed the best extraction efficiency results. These findings may provide a strategy for designing high-performance sorptive phases that could remove hydrophilic and hydrophobic compounds from water and a hypothesis about the driving forces of such processes.