Slow Dynamics of Shape Recovery of Disordered Nematic Elastomers

A loosely cross-linked liquid crystal elastomer (LCE) having a disordered director alignment (polydomain texture) slowly recovers to their original shape from the deformed state in the order of 10(3) s after the imposed field is removed. The mesogen alignment at the cross-linking stage greatly affects the shape recovery dynamics of polydomain LCEs, whereas it has no appreciable influence on the equilibrium characteristics such as the nematic-isotropic transition temperature, degree of swelling, and field-induced strain. The shape recovery of a LCE formed in the polydomain nematic state is considerably faster than that originally prepared in the isotropic state because of the memory effect of the initial director distribution at the cross-linking stage. The relaxation time rapidly increases as the temperature approaches the transition temperatures; this is independent of the initial mesogen alignment during cross linking.