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This study examined the fracture of polymer networks via Brownian simulations with various strain rates. The networks were created from star polymers with different branching degrees and conversion ratios. The results showed that strain and stress at break, plotted against cycle rank, form master curves dependent on strain rate; the fracture characteristics decrease with decreasing strain rate. Despite the interplay of Brownian motion, elongation, and bond scission, the cycle rank dependence is qualitatively similar to that reported previously for energy-minimized networks.

Composite polymer gels with embedded nanosheets deform discontinuously without volume expansion during temperature changes, but the reason behind it is unknown. Here the authors predict theoretically that the deformation results from restrictions which the nanosheets set on the polymer gel.

Although a fundamental problem, the effect of node functionality on network fracture has yet to be clarified. This study performed phantom chain simulations for networks made from star polymer mixtures with different functionalities. The results reveal that the fracture characteristics lie on the master curves if they are plotted as functions of the cycle rank of the network, irrespective of the mixing ratio and the conversion rate.

We recently developed an oxidative aging simulation that combines oxidation kinetics with coarse-grained molecular dynamics. This study examines free radical diffusivity in polymer aging, focusing on its impact on spatiotemporal structures and reaction kinetics. We explored two systems with varying reaction rates and three radical diffusivity levels, observing how changes in diffusivity affect aging. Our findings indicate that while radical diffusivity alters reaction kinetics and structures, it does not fundamentally change the aging scenarios.

Two-dimensional sheet-shaped poly(methyl methacrylate) (2d-PMMA) with crosslinking only in the two-dimensional direction was synthesized via planar polymerization of MMA monomer in montmorillonite (MMT) nanolayers by using γ-ray irradiation, and the samples obtained were characterized by size-exclusion chromatography with a multiangle light scattering (SEC-MALS) and atomic force microscopy (AFM). Our results provided experimental proof that the desired sheet-like polymer was attained and the obtained samples were appropriately characterized, augmenting the previous reports.

Viscoelastic properties of comb-shaped ring (RC) polystyrenes with different branch chain lengths were investigated. Even for the RC sample with short branches, a plateau of the dynamic modulus G^*(ω) was observed, suggesting the intermolecular branch chain entanglement occurred. In the region between the plateau and terminal regions, G^*(ω) was observed with a weaker angular frequency dependence than the terminal relaxation. The G^*(ω) data were analyzed with two models: the comb-Rouse model, in which the structures of RC molecules are taken into account by graph theory, and the Milner-McLeish model for entangled star-shaped polymers.