Journal of Polymer Research最新文献

Polymer nanocomposites combining dielectric properties with controlled conductivity are critical for advanced energy storage applications. This study investigates polyethylene oxide/sodium alginate (PEO/SA) blends reinforced with multi-walled carbon nanotubes (MWCNTs). PEO/SA/MWCNTs nanocomposites were fabricated using solution casting, with TEM confirming uniform dispersion of MWCNTs (diameters: 13.30–22.16 nm) without aggregation. DSC analysis revealed enhanced thermal stability, demonstrated by increased glass transition (T_g ↑ 10%), melting (T_m ↑ 12%), and decomposition temperatures, attributed to strong interfacial interactions. Electrical properties showed a significant improvement in conductivity: threefold (to 2.81 × 10⁻⁹ S.cm^− 1 at 100 Hz) at a concentration of 0.40 wt% MWCNTs, with further improvement at elevated temperatures. Dielectric studies demonstrated exceptional permittivity (ε′ = 1.66 × 10³at a concentration of 0.40 wt% MWCNTs, a 447% increase compared to the pure blend) and frequency-dependent behavior, with both ε′ and ε″ values decreasing steadily before stabilizing above 1 MHz. The loss tangent (Tanδ) demonstrated dual dependency: increasing with MWCNTs concentration/temperature but decreasing with frequency due to reduced interfacial polarization. These results establish PEO/SA/MWCNTs nanocomposites as promising next-generation dielectric materials for flexible energy storage and optoelectronic systems.

This study presents a comprehensive comparative analysis of polysiloxane-based triboelectric nanogenerators (TENGs) incorporating varying loadings of multi-walled carbon nanotubes (MWCNTs) to enhance energy conversion performance. Flexible nanocomposite films were fabricated using the doctor blading method, enabling precise control over film thickness and homogeneity. The triboelectric and dielectric properties of the composites were systematically evaluated across MWCNT concentrations ranging from 0 to 0.1 wt%. Incorporation of MWCNTs markedly improved the electrical performance of the TENGs, achieving an open-circuit voltage (Voc) of 51 V and a short-circuit current (Isc) of 5.7 µA at an optimal loading of 0.05 wt%, representing significant enhancements compared to pristine polysiloxane films (32 V and 3.3 µA, respectively). The improvement is attributed to the establishment of localized conductive networks that facilitate enhanced interfacial polarization and charge transport within the polymer matrix. However, excessive MWCNT content (0.1 wt%) led to nanoparticle agglomeration, forming charge leakage pathways that reduced triboelectric output. Beyond the electrical enhancement, the incorporation of MWCNTs is expected to reinforce the polymer network, improving elasticity, durability, and resistance to mechanical fatigue under repeated operation. This comparative investigation underscores the critical role of nanofiller concentration and dispersion uniformity in simultaneously optimizing the electrical and mechanical properties of flexible nanocomposite-based TENGs. The findings provide valuable insights into the rational design of high-performance, self-powered energy harvesting systems for wearable and portable electronic applications.

Phospholipid-coated chitosan cryogel particles exhibit enhanced mechanical properties, with improved elasticity and durability under compression and release cycles. Among the two coating methods studied, the direct incubation in the liposome solution method resulted in a more effective and higher phospholipid distribution than the solvent evaporation method. Scanning electron microscopy (SEM) analysis confirmed that phospholipid coating smooths the surface and cross-section pores, while the energy dispersive X-ray (EDX) analysis indicated a higher phosphorus atom presence in coated chitosan cryogels coated via incubation. The DPPC (dipalmitoylphosphatidylcholine) membranes facilitate strong interaction with the chitosan matrix, substantiated by the shift of transition temperature (T_m) on differential scanning calorimetry (DSC) results, leading to increased mechanical resilience. Coated chitosan cryogels maintained their structure after five compression and release cycles, compared to the uncoated chitosan cryogels, which deformed irreversibly after four cycles. Furthermore, the surface functionalization of coated chitosan cryogels highlights the significance of coating techniques in optimizing the mechanical performance of cryogels, making them suitable for advanced industrial and biomedical applications.

Intervertebral disc degeneration is a major cause of lower back pain and disability. The development of biocompatible materials for intervertebral disc replacement is crucial for addressing this condition. This study investigated the development of polyvinyl alcohol (PVA)-based composite hydrogels as a potential solution for nucleus pulposus replacement in intervertebral disc repair. Chemically crosslinked PVA hydrogels with varying molecular weights (15,000, 61,000 and 125,000) and Hexakis(methoxymethyl)melamine (HMMM) concentrations were prepared using two different sizes of SiO₂ particles, along with ZrO₂ particles. These hydrogels were characterized for their swelling and mechanical properties. The results indicated that the optimal HMMM concentration for maximizing swelling capacity was 20%. The incorporation of ceramic particles into the hydrogel matrix enhanced the mechanical properties. The study show that the specific particle type and concentration significantly influence the balance between swelling capacity and mechanical strength. For instance, the addition of 5% of the smaller SiO₂ particles (SF600) to PVA with a molecular weight of 61,000 resulted in the highest mechanical strength while maintaining a suitable swelling capacity. The results highlight the potential of these PVA-based composite hydrogels for nucleus pulposus replacement, offering promising avenues for further research and development.

Photothermally responsive hydrogels with robust mechanical properties are highly desirable for biomedical engineering and wearable applications. Here, a simple and scalable strategy is proposed to fabricate multifunctional polyvinyl alcohol (PVA)-based hydrogels by integrating polydopamine (PDA) and citrate-stabilized silver nanoparticles (Ag NPs). PDA provides broadband light absorption and adhesion, while Ag NPs contribute localized surface plasmon resonance (LSPR) effects and improved conductivity. Successive freeze-thaw cycles promote network densification and microcrystalline formation, further reinforcing the hydrogel matrix. Compared to PVA@PDA hydrogels, the optimized PVA@PDA@Ag hydrogel exhibited superior photothermal conversion and mechanical performance, with maximum load, tensile strength, and yield stress increasing by 2.3-fold, 2.5-fold, and 2-fold, respectively. These enhancements result from the synergistic physical crosslinking effect of PDA and Ag NPs on PVA chains, improved charge and thermal transport, and network crystallization. This work offers a versatile platform for the design of high-performance multifunctional photothermal hydrogels.

Heparin-mimicking shape memory polymers (HmSMPs) were synthesized by copolymerizing sodium vinyl benzenesulfonate and sodium acrylate, introducing sulfonate (–SO₃⁻) and carboxylate (–COO⁻) functionalities analogous to natural heparin. Hydroxyapatite (HAp) (1–5 wt%) was incorporated to modulate thermal, mechanical, and biological properties. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the retention of heparin-mimicking groups after filler addition, with the –SO₃⁻ (1072 cm⁻¹)/C = C (1578 cm⁻¹) intensity ratio remaining ~ 1.25 across all composites. Differential scanning calorimeter (DSC) analysis showed a stable glass transition temperature (Tg = 85 ± 2 °C) and ≤ 15% variation in enthalpy change, indicating preserved segmental mobility and thermal actuation consistency. At room temperature, tensile strength increased from ~ 45 MPa (neat) to ~ 50 MPa (2 wt% HAp) due to improved load transfer, while at Tg, strength peaked at ~ 18 MPa for 5 wt% HAp, reflecting effective reinforcement in the softened state. In-vitro assays with Swiss 3T6 fibroblasts revealed enhanced viability (up to 93%) and network formation on HAp-reinforced surfaces, attributed to synergistic effects of HAp bioactivity and heparin-like surface chemistry. These results demonstrate that HmSMP–HAp composites maintain their shape memory performance while offering tunable mechanical strength and improved cytocompatibility, making them promising for biomedical devices requiring anticoagulant-like surfaces and structural integrity at body temperature.

Graphical Abstract

Nanocomposites comprising polylactic acid (PLA), a biodegradable polymer, and graphene (0.5–10 wt%) were prepared through a solvent-based approach to examine the transition from a liquid-like state to a solid-like state as well as the percolation threshold. The characterization of viscoelastic properties, electrical conductivity, and graphene dispersion was conducted utilizing an oscillatory rheometer, direct current electrical measurements, and atomic force microscopy (AFM). The rheological assessments demonstrated an enhancement in both storage (G’) and loss (G’’) moduli in comparison to unmodified PLA, accompanied by a reduced frequency dependence at lower frequencies, signifying a transition to elastic behaviour at 4.4 wt% (2.5 vol%)—the rheological percolation threshold. Electrical percolation was detected at 5.9 wt% (3.4 vol%), with conductivity exhibiting a sharp increase from 10⁻¹¹ to 10⁻³ S/m in the range of 4–6 wt%. AFM analyses verified the uniform dispersion of graphene (thickness of 4.5 nm, diameter approximately 150 nm, aspect ratio roughly 33), whereas the excluded volume methodology estimated the percolation threshold to be at 3 wt% (1.7 vol%). The discrepancies in percolation thresholds arise from differences in inter-particle spacing, with electrical conduction necessitating closer contacts (5 nm) compared to the rheological networking (~ tens of nm). These insights contribute to the advancement of sustainable, conductive nanocomposites intended for biomedical applications, such as shape-memory devices.

The morphological evolution of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction active layers during solvent evaporation represents a critical determinant of organic photovoltaic device performance. This study employs coarse-grained molecular dynamics simulations based on the Martini 3.0 force field to investigate the structural reorganization of P3HT: PCBM: chlorobenzene ternary systems under controlled evaporation conditions. Two distinct solvent removal protocols (1% and 3.75% chlorobenzene removal per step) were systematically evaluated to elucidate their impact on donor-acceptor phase separation and interfacial morphology. The simulation system comprised 75 P3HT chains (degree of polymerization = 48), 526 PCBM molecules, and 2500 chlorobenzene molecules within a 15 × 15 × 44 nm³ periodic simulation box. Structural analysis through radial distribution functions, density profiles, and cluster analysis revealed significant differences in phase separation behavior between the two evaporation rates. Slower evaporation (1% removal) promoted enhanced P3HT chain ordering and more favorable donor-acceptor interfacial contact, while rapid evaporation (3.75% removal) led to kinetically trapped morphologies with reduced structural order. The findings provide molecular-level insights into processing-structure relationships in organic photovoltaic active layers and offer guidance for optimizing solution-processing conditions. Furthermore, the quantitative comparison between slow and fast solvent evaporation provides predictive insights that can guide experimental protocols and bridge the gap between computational modeling and device fabrication.

Silicone rubber (SR), as a unique functional material, has attracted widespread attention and has been applied in various fields, such as soft robotics. Fillers are commonly added to SR to provide it with new functions or enhance its mechanical properties. However, fewer studies have utilized natural fibers as reinforcing materials. Herein, a soft actuator made of modified bamboo fiber (BF)-reinforced SR is designed. The microstructure of modified BF and its impact on SR are analyzed using scanning electron microscopy and Fourier-transform infrared spectroscopy, then the mechanical properties of BF/SR are examined. Additionally, the deformation of the actuator is simulated and experimentally tested. The results show that the BF modified by sodium hydroxide and KH-570 are well dispersed, and exhibit improved interfacial bonding with the SR matrix, leading to enhanced modulus and hardness. Meanwhile, the Ogden 2nd order provides the best fit, and the simulation results and experimental data of soft actuators show good agreement. Soft actuators from modified BF-reinforced SR are significantly enhanced compared to that from pure SR without affecting the ductility required for its normal operation. It not only shows the promising applications of BF/SR polymers, but also indicates the accuracy of the finite element methods for composites and actuators. On the other hand, it also provides a reference for applications of larger sizes of functional fillers in soft actuators.