Photocrosslinked film of polymers having chalconyl moiety and their alignment capability for liquid crystal materials

Abstract

We synthesized side chain polymethacrylate derivatives (polymers 1 and 2), side chain polyimide derivatives (polymer 3 and 4), and main chain polyimide derivative (polymer 5) containing a chalconyl moiety to investigate both the extent of photo-reaction and photo-alignment behavior of liquid crystalline (LC) molecules. A smectic A phase was exhibited for the polymethacrylate derivatives, while polyimide derivatives did not show any mesophases. Only glass transition temperature was observed for the polyimides. Polymethacrylate derivatives showed large values of the extent of photo-reaction in the LC phase, while the extent of photo-reaction for polyimides above glass transition temperature was larger than that below glass transition temperature. Mixtures of low molar mass liquid crystal (MBBA or 5CB) and dichroic dye were filled in the LC cells fabricated from the polymer. In the case of the LC cells fabricated from polymer 1 irradiated with linearly polarized UV (LPUV) light in the LC phase, LC molecules were easily aligned parallel to the electric vector of the incident LPUV light. Parallel alignment behavior of LC molecules was also observed for the LC cells fabricated from the polymers 3 and 4 irradiated with LPUV light, while LC molecules in the LC cells fabricated from the polymer 5 were aligned perpendicular to the electric vector of the incident LPUV light.