Photomechanical properties of azobenzene liquid-crystalline elastomers

摘要

We prepared homogeneously aligned azobenzene liquid-crystalline elastomer (LCE) films with low Tg and explored their photomechanical properties. Upon irradiation with UV light, the films bent toward a light source at room temperature. The mechanical force generated upon exposure to UV light was evaluated by thermomechanical analysis. It was found that the mechanical force generated by photo-irradiation increased with an increase in the cross-linking density. In particular, an LCE film containing 80 mol% azobenzene cross-linker produced a force of over 1 MPa by photo-irradiation, which enabled the film to lift an object 20 times heavier than itself. The degree of contraction by photo-irradiation increased with an increase in temperature and light intensity. Bending could be brought about by more than 5000 times with periodic irradiation. Furthermore, it was found that the LCE films exhibited bending and unbending behaviour by irradiation with sunlight.