State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, 610065, P. R. China.
Scientific Research Institute, Luzhou North Chemistry Industry Corporation, Luzhou, 646100, P. R. China.
Macromol Rapid Commun. 2023 Nov;44(21):e2300354. doi: 10.1002/marc.202300354. Epub 2023 Aug 21.
Adopting only a small amount of azobenzene molecular to design liquid crystal photo-responsive materials capable of quick response and flexible adjustability is in high demand but is challenging. Herein, azobenzenemolecules into polyurethane elastomer containing crystalline structure for preparing azobenzene liquid-crystal elastomers (ALCEs) are demonstrated and this phenomenon of the synergistic effects between liquid crystal and crystalline phase is discovered. The key point of the work is that the synthetic ALCEs can utilize the reversible isomerism capability of azobenzene molecules under light irradiation, which can pry the motion of the macromolecular crystalline region in system to realize the large macroscopic deformation of the photo-responsive behavior. Obviously, the ALCEs sample containing azobenzene molecule and polyethylene glycol crystallization can quickly bend, illuminated by ultraviolet light and rapidly straighten under green light. Under the same ultraviolet irradiation, the bending speed, final bending angle, recovery rate and recovery ratio of ALCEs are larger than that of ALCEs without any crystalline structure. This ALCEs based on the synergistic effects between liquid crystal and crystalline phase can break through the current dilemma that the application of traditional azobenzene photo-responsive materials is limited by their concentration, greatly expanding the design thought and their scope of application.
采用少量的偶氮苯分子来设计能够快速响应和灵活调节的液晶光响应材料是一项高要求但具有挑战性的任务。本文通过将偶氮苯分子引入含有结晶结构的聚氨酯弹性体中，制备了偶氮苯液晶弹性体（ALCEs），并发现了液晶相与结晶相之间的协同效应。这项工作的关键在于，所合成的 ALCEs 可以利用偶氮苯分子在光照射下的可逆异构化能力，撬动体系中高分子结晶区的运动，实现光响应行为的大宏观变形。显然，含有偶氮苯分子和聚乙二醇结晶的 ALCEs 样品在紫外光照射下可以快速弯曲，并在绿光照射下迅速变直。在相同的紫外光照射下，具有结晶结构的 ALCEs 的弯曲速度、最终弯曲角度、恢复率和恢复比都大于没有任何结晶结构的 ALCEs。这种基于液晶相与结晶相协同作用的 ALCEs 可以突破传统偶氮苯光响应材料由于浓度限制而应用受限的困境，极大地拓展了设计思路及其应用范围。
