Photoregulated Liquid Crystal Alignment on Photoreactive Side-Chain Liquid-Crystalline Polymer

Abstract
We describe the anisotropic photoreaction of photoreactive side-chain liquid-crystalline polymers (SLCPs), containing biphenyl mesogen and photoreactive cinnamoyl group, by irradiation with a linearly polarized (LP) UV light, and the alignment behavior of the low-molecular-weight (LMW) liquid crystal (LC) on them. The photo-crosslinked SLCP thin film photoreacted at room temperature showed very small negative dichroism, while that photoreacted in the LC temperature range of the film exhibited positive dichroism. The photoreacted SLCP film can align LMW-LC director \tilden both parallel and perpendicular to the incident \hatE vector of the LP-UV light. The alignment direction of the LMW-LC was controlled by the amount of photoreaction of the cinnamoyl group.