Solubility and molecular alignment behavior of liquid-crystalline polymers by scanning wave photopolymerization

Abstract

Functional soft materials with controlled molecular alignment are attracting much attention in various fields due to their excellent flexibility and functional properties. Among conventional alignment methods, mechanical methods such as rubbing the polymer surface are well-known as a facile route to align various molecules. Besides, photoalignment methods, using photoresponsive molecules and polarized light, enable precise alignment control towards advanced functions. As a novel alignment method combining the advantages of both mechanical and photoalignment methods, we have developed scanning wave photopolymerization (SWaP) where phototriggered molecular diffusion is applied to align molecules. Since it uses the molecular diffusion as a driving force for alignment control, SWaP has the potential to align a variety of molecules. For further exploration of the mechanism, it is necessary to understand the polymer properties; thus, the synthesis of polymers applicable to solution-based analyses is highly desired. In this study, we conducted SWaP to synthesize soluble liquid-crystalline polymer films with one-dimensional alignment. Furthermore, we compared the molecular alignment behavior between SWaP and the conventional rubbing alignment technique using a soluble polymer, and revealed that only SWaP can induce a unidirectional molecular alignment in film.