Brownian simulations for fracture of star polymer phantom networks

According to a recent simulation study [Masubuchi et al., Macromolecules, 56, 9359 (2023)], the cycle rank plays a significant role in determining the fracture characteristics of network polymers. However, the previous studies considered only energy-minimized networks without including the effects of thermal agitation. To address this gap, this study conducted Brownian dynamics simulations at various stretch rates. The results showed that even with Brownian motion, the strain and stress at break obtained for different node functionalities and conversion ratios exhibited master curves when plotted versus the cycle rank. These master curves depend on the strain rate, indicating that the strain and stress at break decrease with decreasing strain rate. The curves are qualitatively similar to those observed in energy-minimized simulations, even though the competition among Brownian motion, elongation, and bond scission affects the fracture process. 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.