Modeling the thermo-responsive behaviors of polydomain and monodomain nematic liquid crystal elastomers

Liquid crystal elastomers (LCEs) are polymeric materials that combine liquid crystal orientation and rubber elasticity. The mechanical responses of LCEs strongly depend on the nematic order and temperature. Developing a thermo-order-mechanical coupling model is important for the engineering applications of LCEs. In this work, we first synthesize both polydomain and monodomain LCEs. The shape change with temperature under a certain stress level is further characterized. In the theoretical part, the Landau–de Gennes model and neo-classical model are combined to construct the free energy density of LCEs. A linear term accounting for the effect of interior stress on nematic–isotropic transition is incorporated into the Landau–de Gennes free energy density, while a macro-order parameter is defined to describe the polydomain–monodomain transition for polydomain LCEs induced by the external force. Comparison between the model predictions and experimental results shows acceptably consistency for both polydomain and monodomain LCEs. Therefore, this work provides an efficient approach to predict the shape change of LCEs in various scenarios.