ICSV26

Liquid crystal elastomers (LCEs) are weakly crosslinked polymers with liquid crystal (LC) moiety. They combine the finite deformability of elastomers with the multi-functionality of LCs. Rather large spontaneous deformations can be produced by thermal, optical and electrical stimuli. They can be used as active soft materials in many applications. However, their mechanical behavior depends strongly on the physical properties of the LC molecules attached to the polymer backbones. We propose a continuum mechanical model that combines the finite elasticity theory with the liquid crystal dynamics. In addition to the mechanical equations, we obtain the governing equations for the LC alignment: the director and the order parameter. The stress-strain relation of LCEs is affected strongly by these internal variables. Thin films of LCEs can bend and vibrate under optical or electrical stimuli due to spontaneous deformations. However, the bending behavior can be quite different from purely elastic materials as the LC alignment can have strong effects on the transversal shear strains. A first order shear strain theory is proposed to model the spontaneous bending and vibration. Through proper design of the LC alignment, we can regulate and control the spontaneous bending and vibration behaviors.