Comparing Photoactuation of an Azobenzene-Doped Nematic Liquid Crystal Polymer through Its Activation Mechanism: Trans-Cis-Trans Reorientation and Photoisomerization

We compare the actuation speeds of the azobenzene-doped nematic liquid crystal polymer (azo-LCP) by examining its activation mechanisms: photoisomerization and trans-cis-trans reorientation (TCTR) (also known as Weigert effect). Both experiments and modeling are carried out in this study to compare the speed of bending and contraction acting on azo-LCP. We identify that the TCTR-based photobending of azo-LCP generated less than half the photostrain in a unit cell than that in the photoisomerization case but involves a larger azo-LCP thickness in triggering photodeformation. Because photodeformation occurs in a deeper region than that in the photoisomerization case, the TCTR-based photobending of azo-LCP exhibits a faster bending speed than the photoisomerization-based photobending of azo-LCP, even though less strain is generated in the TCTR case.