Macromolecular Chemistry and Physics最新文献

Natural rubber (NR) has high elasticity, high tensile strength, and excellent processing performance, but its high flammability limits its application. Adding aluminum diethylphosphinate (ADP) to natural rubber can improve its flame retardancy, but its mechanical properties will be greatly reduced. Therefore, it is still a challenge to improve the flame retardancy of NR while maintaining its mechanical properties. In this study, a new flame retardant synergist mDT@Ni was synthesized, which was compounded with ADP and added with NR to study the effect of the composite system on the flame retardancy and mechanical properties of NR. The results showed that compared with pure NR, the oxygen index of NR composites with 0.75 phr mDT@Ni and 19.25 phr ADP increased from 19.2% to 25.5%, the total heat release (THR) decreased by 21.1%, and the maximum heat release rate (pHRR) decreased by 25.7%. At the same time, its mechanical properties have also been improved; the tensile strength and elongation at break increased by 14.5% and 18.2%, respectively. In addition, the flame retardant mechanism was studied in detail by residual carbon characterization and TG-FTIR test.

Ternary composite dielectric films of PMMA/g-C₃N₄/PVDF were prepared using a simple solution casting method. The small difference in dielectric constant between the graphite phase (g-C₃N₄) and polyvinylidene fluoride (PVDF) reduces local electric field distortion. The g-C₃N₄ is a ditopic nanomaterial with low conductivity and a wide bandgap. This property can significantly enhance the breakdown strength of composites. The amorphous polymer poly(methyl methacrylate) (PMMA) is interspersed within the PVDF molecular chain. This disrupts its orderly arrangement, reducing its crystallinity and decreasing its grain size. The crystallinity of the 60% PMMA/3% g-C₃N₄/PVDF composite film decreased to 23.36%, and the grain size was reduced to 5.6 nm. Meanwhile, the addition of PMMA hindered the movement of mobile charges, reducing the leakage current of the composite material to 5.28 × 10⁻⁷ A/cm² and effectively lowering the probability of breakdown. Research indicates that the breakdown strength of the PMMA/3% g-C₃N₄/PVDF composite material achieves 563.81 MV/m when the PMMA content reaches 50 %, representing an approximately twofold improvement over PVDF. Its energy storage density also reaches 6.58 J/cm³ at this point.

The development of nanocarriers for nucleic acid delivery has gained significant attention as a promising strategy to regulate protein expression. Small interfering RNA (siRNA) is a powerful tool for gene silencing; however, it is rapidly degraded in the human body and cannot passively cross cell membranes due to its size and strong negative charge. To protect siRNA and facilitate intracellular delivery, a spermine-based polyacrylamide with a hydrophobic side chain was utilized as a carrier system. This polymer demonstrated high encapsulation efficiency, forming nanoparticles below 150 nm in size with a slightly positive zeta potential and low polydispersity at N/P ratios of 5 and 7. Additionally, the formulation process proved to be highly reproducible and scalable using a microfluidic mixing method. Moreover, siRNA-polyplexes exhibited good biocompatibility and maintained high cell viability post-transfection. In vitro, they demonstrated strong knockdown efficiency in murine fibroblasts (L929), murine lung epithelial cells (MLE12), human lung adenocarcinoma cells (A549), and human cervix adenocarcinoma cells (HeLa-GFP). Furthermore, the polyplexes promoted rapid cellular uptake and efficient endosomal escape, ensuring effective intracellular delivery. Given the therapeutic potential of siRNA, particularly for diseases lacking effective treatments, this approach holds significant promise for targeting solid tumors and fibrotic disorders.

Catalase is an enzyme that is useful for the degradation of toxic H₂O₂, which has been used for immobilization by using chemically modified polyhedral oligomeric silsesquioxane (POSS) as a support matrix. This work presents a study on the immobilization of catalase on functionalized POSS structure to enhance its stability and performance. The synthesized Cat@Glu@OAPOSS was extensively characterized by using Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), and Field emission electron microscopy (FESEM) to confirm its immobilization and structural integrity. It was observed that 24.8 mg g⁻¹ of catalase was immobilized on the POSS matrix. The developed composite, i.e., Cat@Glu@OAPOSS, was efficiently used for the evaluation of catalytic activity in the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂). By altering the parameters such as pH, Cat@Glu@OAPOSS dosage, TMB, and H₂O₂ concentration were optimized for TMB oxidation. Enzyme kinetics were examined using the Michaelis-Menten plot and the Lineweaver-Burk plot; the findings show that the enzyme-substrate affinity and reaction rate are favorable, with the value of K_m and V_max as 1.05 mM and 0.98 mM sec⁻¹, respectively. The innovative utilization of modified POSS as an immobilization scaffold provides improved enzyme stability and reusability.

In this paper, a novel temperature-sensitive dual self-healing magnetic polyurethane has been developed based on the Diels–Alder (DA) reaction between acrylamide and furfural and the Schiff base reaction between furfural and polyether amino. Unlike other self-healing polymers that require external force, this polymer relies only on magnetic force to close the cross-section, allowing remote control of the polymer without touching it. The polyurethane has a stable structural composition and excellent mechanical properties, exhibiting different properties over a narrow temperature range. By grafting functional groups on the surface of NdFeB to improve the dispersion of NdFeB, the problem of non-uniform dispersion due to NdFeB deposition and aggregation during the polyurethane curing process has been partially solved. The thermal stability of the polymers was determined using a differential scanning calorimeter. The results show that magnetic actuation can make the cross-section tighter than external force. The surface modification of NdFeB effectively improves the aggregation problem of NdFeB and improves the mechanical properties of polyurethane to a certain extent, which has a wide range of applications. Several simple modular magnetic drive models are constructed, which provide examples for more complex magnetic drive models in the future.

The incorporation of nanofillers into biodegradable polymers is an effective approach to improve the physical properties and mechanical performance for various practical applications. In particular, the interfacial microstructure between the polymer and nanofillers plays a critical role in determining the macroscopic properties of the resulting polymer nanocomposite. In this work, we report carbon nanotube (CNT) induced interfacial transcrystallization of poly(L-lactic acid) (PLLA) in the single-fiber composite. The dynamic process of PLLA transcrystallization around the single CNT fiber is investigated under isothermal crystallization in the temperature range from 124°C to 136°C using in situ polarized optical microscopy. Transcrystallization kinetics are analyzed based on polymer heterogeneous nucleation and crystallization theories. The interfacial free energy difference parameter (Δσ/σ = 0.057) and the fold surface free energy (σ_e = 5.82 × 10⁻² J/m²) are calculated to assess the nucleation ability and crystallization barrier, respectively. Atomic force microscope (AFM) analysis reveals radially aligned edge-on lamellar crystals adjacent to the CNT fiber. Alternative transformation from the edge-on lamellar orientation to a flat-on orientation results in a banded transcrystalline texture. A proposed mechanism is presented that lamellar twisting during the crystal growth is attributed to the banded transcrystals.

This study presents a one-pot emulsion polymerization that combines step-growth process of methylene-bis(4-cyclohexylisocyanate) (HMDI) and polyether polyol (EP-330N) to form polyurethane (PU) and chain growth radical polymerization of methyl methacrylate (MMA) and crosslinker ethylene dimethacrylate (EDMA) to produce crosslinked poly(methyl methacrylate) (PMMA). The as-prepared interpenetrating PU-PMMA hybrid latexes have features of tailored cross-linking densities (gel content as high as 49.8%, controlled by the molar ratio of ─NCO/─OH, namely R-value), yielding colloidally stable particles (90–110 nm) with a spherical morphology. FTIR and Soxhlet extraction are employed to characterize the successful synthesis of hybrid particles. As-proof of application, the PU-PMMA particles have been used as a toughening modifier of poly(vinyl chloride) resin (PVC). The impact strength of PVC blends increases from 2.6 to 4.6 kJ/m² with 0–10 phr PU-PMMA addition. These results demonstrate that the one-pot emulsion polymerization integrating radical and step-growth mechanisms could be considered as a straightforward, green emulsification method to synthesize interpenetrating hybrid particles with tunable properties.