Journal of Polymer Science最新文献

This study explores the behavior of the polypropylene/polybutylene succinate (PP*/PBS) polymer blend and its nanocomposites containing varying amounts of organically modified montmorillonite (OMMT) (Cloisite20: C20) (1%, 2%, 3%, 5%, and 10%) when subjected to electron beam irradiation in a scanning electron microscope (SEM). More specifically, we have studied the electrical properties of nanocomposites, in particular the trapping and transport of electrons in the material, as well as the emission of electrons. To examine the storage and spreading of injected electrical charge in nanocomposites under electron irradiation, we used time-resolved current analysis method by measuring the induced currents (displacement and leakage currents). In order to verify whether there is a link between the electrical properties and the dispersion of the nanoclay particles in the polymer matrix, structural analyses were also carried out by x-ray diffraction (XRD). The results revealed a significant increase in the equilibrium trapped charge as the amount of clay nanoparticles introduced into the matrix increased. This trend can be attributed to both an increase in the number of involved traps and the presence of interfaces that act as defect sites. This was checked by determining the energy distribution of the traps using Simmons' approach. Correlating the measured displacement and leakage currents allowed us to demonstrate that the presence of clay nanoparticles leads to a decrease in the electron emission efficiency.

Dielectric elastomer actuators (DEAs) are widely used in many fields such as bionic robotics and wearable electronics. Due to a high elastic modulus and a poor flexibility, pure sodium alginate (SA) film constrains the deflection of DEA and is not suitable for using as the electrode. By incorporating the plasticizer of glycerol and the conductive fillers of oxidized multi-walled carbon nanotubes (MWCNTs), the resultant MWCNT/SA composite film exhibits a high flexibility and a high electrical conductivity (129 Ω·sq.⁻¹), enabling it as the electrode to drive the dielectric matrix of VHB4910 for out-of-plane actuations. Driven by a relatively low electric field of 20.8 V/μm, the MWCNT/SA electrode DEA presents a desired areal strain of 3.8%. Long-term actuations reveal that the MWCNT/SA electrode DEA exhibits very stable electromechanical behaviors with a relative displacement shift (RDS) of 19.8% over 500 cycles, which is far lower than the commercial silicone electrode DEA, whose RDS is 127.8% under the same driven conditions.

Sequential deposition of polymer layers of very diverse characteristics has been applied to produce nanoassemblies of well-controlled thickness and physico-chemical properties. While conventional layer-by-layer approaches are based on the sequential deposition of distinct, mutually interacting materials, nanoassemblies formed by a single, unique polymer are challenged by the need of chemically interacting units to ensure layer-to-layer binding. Here, pyrrolidone and pyridine-containing polymers are mixed with the bifunctional crosslinker 1,6-dibromohexane and sequentially spin-coated as single, neutral polymers. The incorporation of the crosslinker within each deposited layer enables stepwise covalent bond formation while the nanofilm is being assembled. N-alkylation of amine groups by the crosslinker's alkyl halides during thermal annealing post-layer deposition ensures both intra and interlayer crosslinking with a single formulation. Thickness, growth profile, surface roughness, and wettability of the covalently bound nanoassemblies are evaluated together with their interaction with Staphylococcus aureus and HeLa cancer cells. The antibacterial and non-adhesive properties of a set of nanofilms are investigated and discussed in light of the physico-chemical characteristics of the films.

In this study, we examine the biaxial, large, and rapid deformation characteristics of heavy-gauge ABS sheets within the temperature range of 120°C to 160°C, relevant to the industrial forming process. A custom-built bubble inflation apparatus with a 300 mm diameter was designed for this purpose. Temperature uniformity across the sheet was verified using a thermal camera, while the temperature profile through the material's thickness was monitored during the heating using thermocouples near the top and bottom surfaces of the sheet. The bubble inflation test, combined with displacement, strain fields, and deformation rates at different locations, enables detailed characterization of the bubble's shape under large deformation. To address early-stage geometric instabilities due to sagging from thermal expansion, airflow was regulated with a precise flow control valve before inflation, while 3D-DIC monitored the real-time displacements to correct for sag deformation. The inflation pressure profile was recorded and synchronized with 3D-DIC strain evolution data for each test, allowing for analysis of the characteristic stress–strain curve at the pole. By evaluating the material's equi-biaxial properties at the pole and biaxial strain measurements away from the pole, the collected data provides a strong basis for future calibration of constitutive material models through an inverse approach, enabling accurate integration into process simulations.

Flexible piezoresistive pressure sensors, due to their lightweight, bendable, and highly sensitive characteristics, have been widely used in fields such as wearable devices, electronic skin, and intelligent robotics. Besides the development of various high-performance materials, the performance of these sensors is closely related to the design of their surface microstructures. Different surface microstructures can significantly enhance the sensitivity, stability, and durability of piezoresistive sensors. In this paper, three types of flexible thermoplastic polyurethane (TPU)/carbon nanotube (CNT) nanocomposite foam piezoresistive sensors with different surface microstructures and internal porous structures were prepared using supercritical carbon dioxide (sc-CO₂) foaming process. The effects of the three surface microstructures on the piezoresistive sensing performance of TPU/CNT nanocomposite foams were studied in detail. The results show that the foam sensor with a double-ridge surface microstructure exhibits significantly enhanced sensing performance, including high sensitivity (0.309 kPa⁻¹), fast response time (~40 ms), wide working range (0–80 kPa), and stability over more than 600 cycles. Additionally, the prepared flexible piezoresistive sensors can be integrated into smartwatches, fitness bands, and smart clothing, enabling real-time monitoring of heart rate, blood pressure, respiratory rate, and physical activity. This provides precise data support, demonstrating the promising application prospects of these flexible surface microstructure foam piezoresistive sensors in the future.

The excessive accumulation of reactive oxygen species (ROS) on wound surfaces poses considerable challenges to the wound healing process, as it exacerbates inflammation and heightens the risk of skin infections. Consequently, the development of multifunctional dressings that possess both ROS-scavenging and antimicrobial properties is of clinical significance for enhancing wound healing. To address these challenges, we synthesized a dual-scavenging hydrogel utilizing dual-dynamic crosslinking techniques. This hydrogel is composed of poly-lysine-grafted D-glucono-1,5-lactone, dithiodipropionic acid/lipoic acid, and dopamine (PLGDTD), in conjunction with borax. The multifunctional attributes of the hydrogel can be attributed to the incorporation of borate esters, dopamine, and disulfide bonds. Experimental results demonstrate that this hydrogel exhibits a robust antioxidant capacity and a pronounced inhibitory effect against Staphylococcus aureus and Escherichia coli . The results of cellular studies indicate that the hydrogel is capable of effectively scavenging ROS and mitigating oxidative stress, attributable to its dual-scavenging mechanism involving borate and disulfide bonds. This multifunctional hydrogel demonstrates significant potential as a candidate for enhancing wound healing associated with ROS.

To mitigate the strong aggregation and limited solubility observed in the previously reported vinylene-bridged alkoxyfluorobenzothiadiazole (FOBTzE)-based polymer, PFOE4T, we designed and synthesized PBFOE-1. This novel semiconducting polymer, based on the FOBTzE framework, incorporates an alkylthienyl-substituted benzodithiophene (BDT) as the donor unit. PBFOE-1 demonstrated broad and intense absorption between 300 and 700 nm with a relatively wide bandgap of 1.7 eV. Additionally, PBFOE-1 features a low HOMO energy level (−5.43 eV) compared to PFOE4T (−5.23 eV), likely due to the incorporation of weakly electron-donating BDT into the polymer backbone. While the PFOE4T/Y12-based solar cell yielded a modest power conversion efficiency (PCE) of 4.37%, characterized by a short-circuit current density (J _sc) of 13.5 mA cm⁻², an open-circuit voltage (V _oc) of 0.69 V, and a fill factor (FF) of 0.47, the PBFOE-1/Y12 cell exhibited a substantially higher PCE of 10.96%. This improvement is reflected in the enhanced J _sc (23.23 mA cm⁻²), V _oc (0.84 V), and FF (0.56). The superior performance of PBFOE-1 is primarily attributed to its improved solubility and aggregation behavior, promoting a more ordered face-on orientation and optimal blend morphology.

Among the classes of synthetic polymers, disulfide-containing structures offer unique opportunities due to their accessibility to redox chemistry that allows for degradation or reversible disulfide formation and exchange under mild conditions. Here, we examine the role of disulfides in olefin metathesis polymerization, specifically alternating diene metathesis (ALTMET) polymerization, for synthesizing unsaturated polyolefins with embedded disulfides. Our synthetic strategy hinged on the use of α,ω-diacrylate monomers, including those connected by a disulfide unit, via copolymerization by the ALTMET mechanism to yield copolymers containing a range of disulfide content. In addition, the potential impacts of sulfur-ruthenium interactions on the ALTMET process were investigated spectroscopically, while the degradation of the resultant polymers was affected by mild reducing agents. Overall, this study contributes to the development of degradable synthetic polymers using olefin metathesis methods, with an increased understanding of the potential for further use of disulfide groups in such metathesis reactions.