From Molecular Structure to Macroscopic Performance: Insights into Polycarbosilane Curing

Effect of Crosslink Density on the Non‐Isothermal Crystallization Behavior of Polyethylene Vitrimer

Converting polyethylene (PE) into dynamic covalent networks represents a crucial pathway toward achieving sustainability in polyolefins. In this study, PE‐Vitrimers with gradient cross‐link densities were constructed, and their non‐isothermal crystallization behavior was systematically investigated using multiple kinetic models. It was found that the influence of the dynamic cross‐linked network on non‐isothermal crystallization is primarily manifested as a reshaping of the kinetic evolution pathway rather than thermodynamic disruption of the crystal structure. Although the introduction of the cross‐linked network does not alter the inherent orthorhombic crystal system of the PE matrix, the polar cross‐linking nodes enhance the Avrami exponent via heterogeneous nucleation effects and induce anisotropic crystal growth. Meanwhile, the steric hindrance arising from the dense topological network gradually dominates, leading to a monotonic decrease in the overall crystallization rate, accompanied by a global upward shift and a non‐monotonic decrease‐then‐increase evolution of the local crystallization activation energy with conversion. This work elucidates the physical competition mechanism between cross‐link‐induced heterogeneous nucleation and topological constraints, providing important theoretical support for the processing design of semi‐crystalline Vitrimer.

Interplay of crosslinking architecture and interparticle interactions in microgel suspension rheology.

HYPOTHESIS Poly(N-isopropylacrylamide) (PNIPAM) microgels are highly porous polymer networks whose mechanical properties are governed not only by environmental factors but also by their internal architecture. We hypothesize that the internal structure of microgels, together with interparticle interactions, synergistically regulates the macroscopic rheological behavior of microgel suspensions. EXPERIMENTS Frequency-sweep measurements were performed to identify the suspension states, evaluate shear-induced structural breakdown and recovery, and monitor continuous volume phase transitions under different conditions. The correlation between the loss tangent (tan(δ)) and the low-frequency power-law viscoelastic exponents were further analyzed. Critical transition points extracted from temperature sweeps were used to construct phase diagrams, describing phase distributions and transition pathways governed by temperature, concentration, and salt. FINDINGS Crosslinking architecture markedly altered the thermal response pathway of PNIPAM microgel suspensions and determined their ability to recover after shear-induced structural breakdown. Salt addition reshaped phase-transition pathways by screening electrostatic repulsion, while simultaneously amplifying architecture-dependent rheological differences among suspensions. These findings confirm that microgel suspension rheology is governed by the coupling between internal crosslinking architecture and interparticle interactions.

Tailoring the Topological Dynamics of Polyethylene Vitrimer Through Stoichiometric and Catalytic Synergy

Designing polymer networks that allow independent control of room‐temperature rigidity and high‐temperature rheological behavior is essential for material recycling. To address physical constraints within semi‐crystalline polyolefins, we constructed polyethylene‐based vitrimers with varying crosslinker ratios and catalyst concentrations via in situ reactive melt blending. Results reveal that large physical spacing in loosely crosslinked networks restricts topological rearrangement. However, combining an equimolar crosslinker ratio with 15 mol% catalyst overcomes these constraints, achieving the lowest activation energy of 94.53 kJ/mol. While increasing the catalyst to 20 mol% plateaus the activation energy at 95.44 kJ/mol, it continues driving the initial static network's densification. Moreover, networks deviating from the equimolar ratio release enhanced local segmental mobility via single‐ended dangling chains, endowing the material with exceptional mechanical recovery. This work provides deep insight into the synergistic regulation between crosslinker and catalyst. It achieves a high degree of decoupling between structural rigidity and rheological activity, offering a core design paradigm for tailored, recyclable polyolefin networks.

Time dependent properties of polymer blends and composites: a review

Polymer blends and composites play crucial roles across aerospace, automotive, energy and structural applications, yet their long-term performance governed by complex time‐dependent properties and performance. Existing reviews often isolate chemical aging, mechanical behavior or characterization techniques, leaving a gap in understanding how molecular‐scale changes translate into macroscopic property loss. This review provides an integrated, mechanism‐driven synthesis of time‐dependent behavior in polymers, linking degradation chemistry, morphology evolution and property deterioration. We critically examine physical aging, photo‐oxidation, hydrolysis, viscoelastic relaxation, interfacial decay in composites and the role of environmental stressors. Quantitative trends from the literature are consolidated to clarify how mechanical strength, elongation, thermal transitions, dielectric response, and optical performance evolve. We also evaluate advanced analytical methods, including DMA, dielectric spectroscopy, thermally stimulated depolarization current and nanoscale dielectric tools that reveal molecular mobility and relaxation phenomena. Finally, we outline design guidelines and future directions, emphasizing predictive modeling, nanofiller‐based stabilization and the development of sustainable, long‐life polymer systems.

Fusion kinetics and thermomechanical behavior of Ni–Pd core–shell nanoparticles: insights from molecular dynamics simulations

Computational exploration of the structure and mechanical behaviour of hybrid epoxy-acrylate dual-cure systems.

Wavelength-selective dual-cure epoxy-acrylate polymers have recently been demonstrated experimentally as a platform for generating large mechanical contrasts from a single material system for additive manufacturing [Kim et al., Nat. Mater., 2025, 24, 1116-1125], motivating the need for a molecular-level understanding of how network structure and crosslinking governs the mechanical response in such hybrid systems. Here, we use coarse-grained molecular dynamics simulations to investigate the structural, thermal, and mechanical evolution of a model hybrid epoxy-acrylate network spanning elastomeric and thermoset regimes. By systematically varying network architecture, chain length, bond stiffness, and epoxy conversion, we show that elastomer stiffness is highly sensitive to the topology of the initial acrylate network, whereas thermoset stiffness becomes largely insensitive to these structural details once dense epoxy connectivity is established. Tracking network evolution across epoxy conversion reveals a transition that emerges beyond approximately 40% epoxy crosslinking, after the formation of a system-spanning elastomeric network, where network topology becomes increasingly heterogeneous and deformation mechanisms shift from predominantly entropic elasticity to energy-dominated load transfer involving localized covalent bond stretching. This crossover marks the onset of thermoset-like load transfer, with subsequent crosslinking further strengthening this response as stiffness and bond-level deformation increase smoothly. Together, these results provide a framework for understanding how mechanical contrast in wavelength-selective dual-cure polymer networks emerges from the interplay between elastomeric network topology and a connectivity-driven crossover in deformation mechanisms induced by epoxy crosslinking.