Macromolecular Chemistry and Physics最新文献

A bio-based vanillin–guaiacol cyanate ester (VGCE) resin was synthesized, and its curing behavior was analyzed using non-isothermal DSC at heating rates of 2–25°C min⁻¹. The curing temperature increased with heating rate, and kinetic evaluation yielded activation energies of 69.71 kJ mol⁻¹ (Kissinger) and 73.68 kJ mol⁻¹ (Ozawa), confirming high reactivity and reliability of the model-free approach. The curing profiles were well described by the Kamal–Sourour autocatalytic model, indicating strong autocatalysis and providing consistent kinetic parameters. The catalytic influence of transition-metal acetylacetonates (Cu²⁺, Co²⁺, Fe³⁺, V⁴⁺) was examined, with Cu(II) at 3 wt.% producing the greatest reduction in polymerization temperature (142°C) and activation energy (50.69 kJ mol⁻¹) while maintaining curing enthalpy, demonstrating accelerated network formation. TGA revealed high thermal stability for neat poly(VGCE) (T_dⁱ = 319°C, T_d¹ = 337°C, char yield = 38.3%), attributed to its aromatic triazine structure. Metal incorporation further increased char yield (up to 45.4%), indicating improved thermo-oxidative resistance. Crosslink density increased from ϑ ≈ 0.00524 to 0.00554 mol cm⁻³ upon Cu catalysis, consistent with higher gel content (96.9% → 98.6%) and enhanced network development. Both neat and Cu-catalyzed VGCE exhibited excellent hydro-stability with minimal moisture uptake and maintained desirable dielectric characteristics, with the neat resin showing low-k behavior (ε′ = 2.94). Overall, the metal-catalyzed VGCE systems demonstrate strong potential as sustainable, high-performance thermosetting resins with tunable curing kinetics, thermal stability, and functional properties.

With the development of miniaturization and integration of electronic devices, heat dissipation has become one of the key issues in the electronic industry. Polymer composites with segregated structure have high thermal conductivity at low content of fillers. However, the weak interactions between matrix and fillers may destroy the mechanical property. In this work, the reversibly cross-linked polythiourethane microspheres (PTUM) are prepared; boron nitride (BN) and carbon nanotubes (CNTs) are respectively treated with different silane coupling agents to enhance the interaction with PTUM. Then, a special mixing method (heated at 60°C for 10 min and then mechanically mixed for another 20 min) is applied to further make hybrid fillers adhering tightly to the surface of PTUM. The composites show excellent thermal conductivity (0.96 W·m⁻¹·K⁻¹) and mechanical properties (elongation at break of 696%, tensile strength of 7.3 MPa, and toughness of 24.1 MJ/m³) due to the modified hybrid fillers and segregated structure. Moreover, the composites can be effectively reprocessed due to dynamic bonds exchange. This work supplies a new method for preparing reversibly cross-linked composites with a combination of high thermal conductivity and mechanical property, showing broad applications in flexible electronic devices.

This study investigates the microscale dual-diffusion process of polyacrylonitrile (PAN) solutions in the coagulation bath and the process of PAN fiber formation. The interaction peaks assignment between solvent and water were identified by analyzing the Fourier transform infrared spectroscopy (FTIR) characteristic peaks of red or blue shift. The time-resolved attenuated total reflection FTIR technique was employed to analyze the dual-diffusion process. Enabling quantitative determination of diffusion coefficients based on Fick's second law. A correlation was established between diffusion coefficients, the microstructural characteristics of PAN membranes and the cross-sectional morphology of PAN nascent fibers. Additionally, examination of the microstructure of triple times stretched PAN nascent fibers revealed the formation mechanism of fibers with “Fibrils Within a Filament”.

Employing 3,3',5,5'-tetraisopropyl-[1,1'-biphenyl]-4,4'-diamine and six para-R substituted 2,6-bis(benzhydryl)phenylamines (R = Me, ⁱPr, OMe, OCF₃, Cl, F), a series of bis(arylimino)acenaphthene-nickel (II) bromides, [1-[2,6-{(C₆H₅)₂CH}₂-4-R-C₆H₂N]-2-[4'-NH₂-3,3',5,5'-{(CH₃)₂CH}₄-1,1'-(C₆H₂)₂-C₂C₁₀H₆]NiBr₂ (Ni1, Ni2, Ni4−Ni7) along with our previous two relative nickel complexes Ni3 and Ni8 (R = ^tBu, NO₂), has all been synthesized in good yields and well characterized by FT-IR, EA and X-ray diffraction measurements. The molecular structures of nickel complexes indicate that the large steric hindrances of N-aryl groups build nest for core nickel in axial position. In the presence of AlMe₃ or Me₂AlCl, all nickel complexes exhibit high activities with a maximum activity up to 15.1 × 10⁶ g (PE) mol⁻¹ (Ni) h⁻¹, producing high-molecular-weight polyethylenes (M_n:2.9−9.2 × 10⁵ g mol⁻¹) along with narrower dispersities (PDI: 1.9−2.4). All polyethylenes obtained are highly branched with the branching content strongly affected by the combination of the structural complexes and the co-catalyst employed. Moreover, the resultant polyethylenes perform excellent elastic properties, being polyethylene elastomers (PEE) as newly promising thermoplastic elastomer (TPE).

Understanding the energetic disorder in polymeric organic semiconductors is critical for optimizing their charge transport properties in photoconductive and optoelectronic devices. In this study, we systematically investigated the influence of molecular weight on the density of states (DOS) and photorefractive (PR) performance of poly(N-vinylcarbazole) (PVCz)-based composites. Photoelectron yield spectroscopy (PYS) revealed that the energetic disorder, characterized by the deviation of the DOS (σ_DOS), decreases with increasing PVCz molecular weight, despite the HOMO energy level remaining constant. Photorefractive performances showed that diffraction efficiency increases and response time decreases with increasing molecular weight, exhibiting a strong correlation with σ_DOS. Thermal and structural characterizations—including glass transition temperature (T_g), X-ray diffraction (XRD), density (ρ), and fractional free volume (FFV)—demonstrated that σ_DOS is most strongly correlated with T_g (R² = 0.931), suggesting that chain rigidity and packing density are key factors influencing energetic disorder. The Gaussian disorder model (GDM) was applied to estimate carrier mobility, further validating the DOS-derived transport trends. This work establishes T_g as a practical and predictive proxy for σ_DOS, offering a simple and effective approach for evaluating energetic disorder in polymeric semiconductors. Our findings provide a framework for the rational design of PR materials and extend to broader applications in organic electronics.