Journal of Polymer Research最新文献

The effect of graphene oxide (GO) on the morphology and properties of monomer casting polyamide 6/polystyrene (PA6/PS) alloy was evaluated. PA6/PS/GO ternary alloys were prepared by the double in situ polymerization of ε-caprolactam and styrene monomer. SEM results show that phase inversion occurred in this system when the GO content was 0.5 wt%. A morphology of PA6 microsphere dispersed phase/PS matrix was formed. TEM results show that the GO lamellae were selectively and homogeneously dispersed in PA6 microspheres. When the GO content reached 1 wt% or 1.5 wt%, the system did not reverse completely, forming a structure of PA6 block or PA6 network continuous phase and local PA6 microsphere dispersed phase/PS continuous phase. GO lamellae were dispersed in PA6 blocks or PA6 network continuous phases. With the increase in the molecular weight of PS in PA6/PS/GO alloy, when the GO content reached 1.5 wt%, the system still maintained the morphology of PA6 microspheres. A larger molecular weight of PS is good for phase inversion, while GO inhibits the phase inversion of PA6/PS alloy. GO lamellae always distributed to the PA6 phase no matter which phase it was predispersed. XRD and DSC spectra show that GO can slightly affected the crystallization of PA6, decreased the crystallization rate of PA6. The antibacterial test results show that the alloy containing 1 wt% GO has an antibacterial rate of up to 95% against Escherichia coli. This selective dispersion phenomenon is of great significance for the study and application of the compatibility of polymer alloy phases.

Phenolic Impregnated Carbon Ablator (PICA) remains a cornerstone of carbon-based Thermal Protection Systems (TPS), yet its performance in extreme hypersonic environments is often limited by oxidation and mechanical erosion. This study develops three novel variants of compression-molded conformal PICA, reinforced with Ultrahigh Temperature Ceramics (UHTCs) ZrB₂ and SiC and subsequently surface-modified with Polycarbosilane (PCS) and Organopolysilazane (OPSZ). Mechanical testing and morphological analysis via SEM were conducted to evaluate the synergistic effects of these modifications on structural integrity and ablation resistance at heat fluxes of 2 and 4 MW/m². Results reveal a significant reduction in linear ablation rates, with PCS and OPSZ variants achieving 0.060 mm/sec and 0.068 mm/sec, respectively, representing a 23 ~ 28% improvement over bare PICA at 4 MW/m². Crucially, microstructural analysis reveals that the surface modification promotes a transition from erosion-dominated recession to a diffusion-limited oxidation regime. This is attributed to the synergistic formation of a coherent, silicon-rich ceramic protective layer (SiO_X, SiO₂) that densifies the surface and anchors the UHTC particles, effectively shielding the underlying carbonaceous fibrous network from severe ablation plumes. These findings provide a scalable methodology for tailoring lightweight, high-performance ablators for next-generation aerospace missions.

In this work, composite nonwoven materials based on a polyimide derived from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA), filled with polytetrafluoroethylene (PTFE) particles, were fabricated via electrospinning from aqueous solutions. The use of a water-soluble salt of polyamic acid (SPAA) as a precursor enabled the preparation of stable spinning solutions and allowed thermal imidization to be carried out at a relatively low temperature of 300 °C. The introduction of PTFE nanoparticles (0–7 wt.%) resulted in the formation of fibers with diameters ranging from 0.9 to 1 µm and a heterogeneous morphology. The investigations showed that the addition of PTFE enhances the thermal stability of the composites, although it causes a slight decrease in their tensile strength and elastic modulus. A key finding is the achievement of an ultra-low dielectric constant (ε), which decreased from 1.55 for the neat polyimide to 1.3 for the composite with 7 wt.% PTFE. The optimal balance of dielectric (ε = 1.4), mechanical, and thermal properties was demonstrated for the composite containing 3 wt.% PTFE. The obtained materials are promising for applications in high-frequency flexible electronics, microelectronics, and the aerospace industry.

This study reports a general synthetic strategy for redox-responsive gels and porous polymers incorporating disulfide bonds. Network polymers were prepared via ring-opening addition reactions of multifunctional epoxides or a trifunctional isocyanate with dithiodicarboxylic acids or a disulfide-containing diol, affording mechanically tunable gels. The elastic modulus of the networks depended on the alkyl chain length of the disulfide crosslinkers and the extent of reaction conversion. Porous polymers were obtained through polymerization-induced phase separation in the addition reactions of a trifunctional aziridine or a trifunctional isocyanate with dithiodicarboxylic acids, yielding interconnected particle-based or co-continuous monolithic morphologies with controllable feature sizes and mechanical properties. All gels underwent efficient reductive degradation in the presence of dithiothreitol, while oxidative conditions enabled regeneration of the network structure, demonstrating reversible crosslinking. Notably, a disulfide-containing gel exhibited electrochemically triggered degradation. These results demonstrate a versatile platform for designing redox-degradable and reconfigurable polymer networks and porous materials with tunable structures and functions.

As weak properties of polymer blends may be attributed to phase separation and low compatibility of a dispersed polylactic acid (PLA) phase in the polyethylene glycol (PEG) matrix, this study reports on the role of TiO₂ nanoparticles (NPs) on property enhancement of PEG/(PLA-TiO₂) nanocomposites. After the synthesis of rutile TiO₂ NPs (40 to 80 nm), the nanocomposites were prepared by solution casting of PEG and (PLA-TiO₂) having a ratio PEG/PLA = 70/30 and 0, 1, 3, and 5 wt.-% TiO₂ NPs. The TiO₂ NPs improve phase dispersion and interfacial adhesion in parallel with an increase in crystallinity, degradation temperature and melting temperature towards maximum values at a concentration of 3 wt.-% TiO₂. The ultraviolet absorption was enhanced, and the optical bandgap energy progressively reduced from 4.21 eV to 2.82 eV at 5 wt.-% TiO₂. Rheological tests showed a sixfold increase in storage modulus, indicating strong elastic behaviour in parallel with a stable solid-like region between 10 and 60 °C and a gel-like transition between 70 and 80 °C. Antibacterial tests showed the highest activity at 1 wt.-% TiO₂ against E. coli and S. aureus. Findings confirm that the PEG/PLA nanocomposites with TiO₂ NPs maintain enhanced thermal stability, ultraviolet shielding, antibacterial activity and mechanical strength, being promising for biomedical, environmental, or packaging applications.

Carboxylated natural rubber-(XNR)/acrylonitrile butadiene rubber (XNBR) reinforced Carbon black (CB)-Silanized Silica (SS) compositions were prepared and cured with sulfur(S) and peroxide (DCP) at 160 °C separately. The cure, chemical and mechanical properties etc. were systematically studied. A low content of XNBR in the blend (BL) resulted in better physico-mechanical properties. The best composition KC3 (30 phr XNBR and 70 phr XNR-Sulfur cured) recorded a bound rubber content, BR (%) of 37.5% with lower t₉₀(high cure rate) compared to KC6(50phr XNBR and 50phr XNR-DCP cured), which recorded BR (%) ~ 17.5%. Interestingly, KC6 recorded the highest crosslinking density (N), torques (M_H and ∆M) and hardness. For instance, KC6 recorded over 109, 98, 230, 35 and 1151% increments in M_H, ∆M, modulus at 300% (M300), hardness (Shore A) and N respectively compared to KC3. However, KC3 exhibited 28, 68, 240%, and 1,399,900% increments in wear resistance, stress, strain (%) and fatigue respectively, as compared to KC6. While the improvement in KC3 was due to the presence of stronger network structures like —BL—S_x—BL—CB—S—SS—BL in addition to interactions like hydrogen (—C ≡ N----H—O) and polar (^ẟ+C ≡ N----O^ẟ+—H)), that of KC6 was mainly linked to weak and physical networks.

In this study, Fe₃O₄ nanoparticles were utilized as stabilizers to construct a Pickering emulsion system for the copolymerization of styrene (St) and acrylamide (AM). The emulsion stability was systematically optimized by varying the Fe₃O₄ nanoparticle concentration in the range of 0.09–0.16 wt% and adjusting the oil-to-water ratio. A comparative study was carried out to evaluate the effects of an oil-soluble initiator AIBN, versus a dual-initiator system comprising AIBN and ammonium persulfate (APS) on the copolymerization kinetics. The successful synthesis of St-AM copolymer in the composite was confirmed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) revealed that introducing APS significantly enhanced the thermal stability of the resulting composite. Specifically, the temperature corresponding to a 5% weight loss (T₅%) increased from 130 °C to 228 °C, while the residual char yield at 800 °C reached 14.43%. Scanning electron microscopy (SEM) further demonstrated that the composite matrix contained uniformly embedded spherical microparticles with well-defined dimensions. These results validate the successful polymerization of the nano-Fe₃O₄-stabilized St /AM Pickering emulsion using the AIBN/APS dual-initiator system, leading to the formation of styrene /acrylamide composite microspheres. This study provides valuable experimental insights and process references for developing novel polymer composites.

In this study, polyurethane foams (PUFs) were reinforced with molybdenum trioxide (MoO₃) nanoparticles to enhance their mechanical, thermal, and flame-retardant properties. Nanocomposite foams were fabricated by incorporating MoO₃ at varying loadings (5, 10, and 15 wt%), resulting in a notable 36% increase in compressive strength at the highest concentration. Thermogravimetric analysis indicated a significant improvement in thermal stability and flame retardancy, with the residual mass at 700 °C rising from 9% to 23% and the maximum weight loss decreasing to 1.1%. These enhancements suggest that MoO₃-filled PUFs offer promising potential for use in fire-sensitive and durability-critical applications such as construction, automotive, and aerospace sectors.

Porous films based on curcumin-loaded chitosan-grafted graphene oxide (CCGO) were developed as potential wound healing materials. The chemical constitution and microstructure of the films were characterized using FTIR, XRD, SEM and EDX analysis. Among the developed films, the CCGO film containing 0.6 wt% curcumin exhibited a pore diameter of 485 μm, a porosity of 79.45 ± 2.92%, a swelling capacity of 306 ± 5.6%, a water retention ability of 360 ± 6.67%, and a controlled biodegradability of 88 ± 2.66%. Due to the presence of curcumin, the CCGO films exhibited antimicrobial activity, showing inhibition zones ranging from 14 to 22 mm against Gram-positive and Gram-negative bacteria, and 0–22 mm against fungi, when compared to the control chitosan-grafted graphene oxide (CGO) film. Cytotoxicity studies confirmed that the CCGO films were non-toxic to the C3H10T1/2 cell line, regardless of their curcumin content. Furthermore, in vitro scratch assays revealed that the CCGO film containing 0.6 wt% curcumin promoted complete (100%) cell migration, proliferation, and wound closure within 12 h, compared to the CGO film. These findings suggest that CCGO films could serve as potential materials for wound healing applications. This work differs from previous studies on curcumin, chitosan, or graphene oxide (GO) by developing CCGO films that exhibit synergistic enhancements in structure, antimicrobial activity, and wound healing potential.

Dynamic hydrogels serve as promising wound dressings by mimicking extracellular matrix (ECM) structures to regulate tissue hydration and oxygen permeability. In this study, a dynamic OG-ACMC hydrogel was synthesized via a Schiff base reaction between periodate-oxidized gellan gum (OG) and ethylenediamine-modified carboxymethyl chitosan (ACMC). Structural changes in oxidation, amination, and crosslinking processes were characterized, and the effects of designed OG/ACMC volume ratios (0.5:1–2:1) on morphologies and physicochemical and biological properties were investigated. Results demonstrated that C = N was successfully formed for achieving dynamic crosslinking, and the hydrogels exhibited a three-dimensional architecture with interconnected pores formed by stacked polymer lamellae. The morphological evolution of the lyophilized scaffolds, from fragile to stable porous architectures, was quantitatively correlated with a significant increase in crosslinking density. Increasing the OG/ACMC ratio densified the network, prolonged gelation time from 75.5 ± 3.2 s to over 300 s, and reduced the equilibrium swelling ratio at the 2:1 formulation while maintaining high and stable water vapor transmission rates. All hydrogels exhibited selective antibacterial activity, achieving up to 83.4% bactericidal rates against S. aureus but none against E. coli; L929 fibroblasts maintained 90.7–99.3% viability, confirming non-cytotoxicity of these hydrogels. After 72 h, they promoted cell proliferation with viabilities of 101.95–103.98% and healthy spindle morphology. Notably, the 1:1 OG/ACMC ratio hydrogel additionally exhibited good injectability, shape adaptability, and self-healing capability. It also demonstrated elastic-dominated rheological behavior (G’ > G’’), as well as stimuli-responsive degradation accelerated by vibration and delayed by Ca²⁺ chelation. These combined properties established the OG-ACMC dynamic hydrogel as a promising multifunctional wound dressing, with the 1:1 ratio demonstrating superior performance.