Xia Yu, Zhang Xinyue, Yang Shu
Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA, 19104, USA.
Angew Chem Int Ed Engl. 2018 May 14;57(20):5665-5668. doi: 10.1002/anie.201800366. Epub 2018 Apr 19.
Liquid crystal elastomers (LCEs) with intrinsic anisotropic strains are reversible shape-memory polymers of interest in sensor, actuator, and soft robotics applications. Rapid gelation of LCEs is required to fix molecular ordering within the elastomer network, which is essential for directed shape transformation. A highly efficient photo-cross-linking chemistry, based on two-step oxygen-mediated thiol-acrylate click reactions, allows for nearly instant gelation of the main-chain LCE network upon exposure to UV light. Molecular orientation from the pre-aligned liquid crystal oligomers can be faithfully transferred to the LCE films, allowing for preprogrammed shape morphing from two to three dimensions by origami- (folding-only) and kirigami-like (folding with cutting) mechanisms. The new LCE chemistry also enables widely tunable physical properties, including nematic-to- isotropic phase-transition temperatures (T ), glassy transition temperatures (T ), and mechanical strains, without disrupting the LC ordering.
具有固有各向异性应变的液晶弹性体（LCE）是传感器、致动器和软机器人应用中备受关注的可逆形状记忆聚合物。LCE的快速凝胶化对于固定弹性体网络内的分子有序排列是必需的，这对于定向形状转变至关重要。基于两步氧介导的硫醇-丙烯酸酯点击反应的高效光交联化学方法，使得主链LCE网络在暴露于紫外光时几乎能瞬间凝胶化。预排列的液晶低聚物的分子取向可以忠实地转移到LCE薄膜上，从而通过折纸（仅折叠）和类似kirigami（切割折叠）机制实现从二维到三维的预编程形状变形。这种新的LCE化学方法还能实现广泛可调的物理性质，包括向列相到各向同性相的转变温度（T）、玻璃化转变温度（T）和机械应变，而不会破坏液晶有序性。
