Topology and fracture of model polymer networks

Toughening of network polymers like rubbers or gels is one of the most important problems in polymer science. While novel types of tough gels have been developed in the last decade, the toughening mechanism is not so clear: most researchers pay much attention to chain length heterogeneity, but little attention to other aspects. In this study, we focus on network topology, which is believed to be essential in complex network. We created macroscopic polymer models made of rubber strings and connecters, and performed fracture experiments of such model polymers with different topological structures. We found that periodic but systematic modifications in local coodination number with keeping the constant mean number (4, in 2D) exhibited great improvement in toughness compared with regular square lattices. In our talk, we will explain the details of our experiments and discuss the results by comparing with numerical simulations and theory.