Photo-induced periodical swing deformation of multiple hydrogen bonds crosslinked liquid crystal elastomer

Abstract

Photo-responsive liquid crystal elastomers (LCEs) can transform the changes in the microstructure and order of liquid crystals into macroscopic deformation, and have attracted wide interests in the fields of soft robotics, biomaterials, nanotechnology, etc. In this article, we purposed a strategy to prepare LCEs with photo-induced periodical swing deformation by using the high glass transition temperature and photo-thermal effect. To implement this strategy, we designed and synthesized azobenzene LCEs with different glass transition temperature, and their deformation behavior was studied in detail. The results showed that the uniaxially oriented azobenzene LCE fiber with low glass transition temperature exhibited reversible photo-induced deformation behavior under alternating irradiation of 365 nm and 470 nm light. However, the uniaxially oriented azobenzene LCE fiber with high glass transition temperature showed photo-induced periodical swing deformation. When irradiated with 365 nm UV light, LCE fiber bent to light. Then the fiber bent away from the light when irradiated with 470 nm light. When the 470 nm light source was removed, the fiber return to bent state. Therefore, the periodical swing deformation of LCE fiber was realized by periodically turning on and off 470 nm light. We also confirmed that this unique photo-induced periodical swing deformation is attributed to the high glass transition temperature and photo-thermal effect of azobenzene LCEs.