Slow stress relaxation in liquid crystal elastomers and gels

Abstract

Randomly disordered (polydomain) liquid crystalline elastomers align under stress above the structural glass transition T_g to form a monodomain. We study the dynamics of stress relaxation during the polydomain–monodomain (P–M) transition analysing the results using the spin-glass nematic order concept. The results for different materials show a universal ultra-slow logarithmic behaviour, especially pronounced in the region of the P–M transition. The data are approximated very well by an equation σ(t)∽σ_eq(ε)+A/(1+α ln t). We propose a theoretical model of self-retardation based on the concept of cooperative mechanical resistance for the re-orientation of each domain, attempting to follow the soft-deformation pathway.