Molecular Simulations Shed Light on Supersoft Elasticity in Polydomain Liquid Crystal Elastomers

Abstract

Liquid crystal elastomers (LCE)—polymer networks constructed with liquid crystal units—are functional materials characterized by a pronounced coupling between elastic strain and liquid crystalline orientational ordering. When prepared by polymerization and cross-linking in the isotropic phase, and then cooled (“isotropic genesis”), a polydomain LCE presents an extraordinary “supersoft” elastic behavior under unidirectional pulling, with a plateau-like low elastic modulus region in the stress–strain curve, before turning into a monodomain LCE where a standard elastic resistance is recovered. The physical mechanism of this behavior is of great interest, but still mysterious. This work investigates its origin, reproducing the experiment and succeeding to observe the plateau-like stress–strain behavior by means of large-scale molecular iso-stress Monte Carlo simulations. The results not only show that the basic molecular mechanism behind supersoft elasticity hinges on local domain rotation and growth but also...