Programmable Complex Shape Changing of Polysiloxane Main-Chain Liquid Crystalline Elastomers

Abstract

Liquid crystal elastomers (LCEs) are shape-morphing materials whose large and reversible shape transformations are caused by the coupling between the mobile anisotropic properties of liquid crystal (LC) units and the rubber elastic of polymer networks. Their shape-changing behaviors under certain stimuli are largely directed by the LC orientation; therefore, various strategies have been developed to spatially modulate the LC alignments. However, most of these methods are limited as they require complex fabrication technologies or have intrinsic limitations in applicability. To address this issue, programmable complex shape changes in some LCE types, such as polysiloxane side-chain LCEs, thiol-acrylate main-chain LCEs, etc., were achieved by using a mechanical alignment programming process coupled with two-step crosslinking. Here, we report a polysiloxane main-chain LCE with programmable 2- and 3D shape-changing abilities that were created by mechanically programming the polydomain LCE with two crosslinking steps. The resulting LCEs exhibited a reversible thermal-induced shape transformation between the initial and programmed shapes due to the two-way memory between the first and second network structures. Our findings expand on the applications of LCE materials in actuators, soft robotics, and smart structures where arbitrary and easily programmed shape morphing is needed.

Liquid crystalline elastomer self-oscillating fiber actuators fabricated from soft tubular molds

“…When being heated above or cooled below T ni , the LCE network varied between the liquid crystal phase structure and the isotropic phase, leading to reversible shape morphing of the LCE materials. In addition, the deformation behaviors of HF-LCEC and WF-LCEC arose from the two-way shape memory instinct of LCE materials synthesized via two-step crosslinking; 64–69 they can perform reversible shape morphing between the initial shapes formed during the first step of crosslinking and the programmed shapes, which are fixed by the second step of crosslinking upon the application of stimuli. Fig.…”