Preparation, characterization, and photo-induced liquid crystal alignment of polyimide and poly(vinyl cinnamate) blend alignment layer

Abstract

In this paper, the preparation, characterization, and photo-induced liquid crystal (LC) alignment of a polyimide (PI) derived from cyclobutane di anhydride and 2,2-bis(4-aminophenoxyphenyl)propane, and a poly(vinyl cinnamate) (PVCi) blend alignment layer are reported. Microscopic and thermal analyses revealed the miscibility of the two components in the thin layers. The occurrence of photo-dimerization and the development of structural dichroism in the blend layers were confirmed from ultra-violet (UV) spectroscopic investigations. The photo-dimerization reaction of the cinnamate was not significantly influenced by the addition of PI into PVCi. The blend alignment layers provided uniform LC alignment, and better thermal stability of LC alignment compared to the pure PVCi alignment layer. The increase of the thermal imidization temperature was found to enhance the thermal stability of LC alignment, which indicates that the increase of T-g by introducing PI to PVCi is responsible for the improvement of the thermal stability of LC alignment.