Photo-induced Liquid Crystal Alignment on Imide Oligomers containing Cinnamate Group

Abstract

In recent years, a considerable amount of research has been directed towards photo-induced liquid crystal (LC) alignment. This technique uses the exposure of a polymer film to polarized UV for developing a structural anisotrophy on its surface. As a result of the anisotropic interaction between the LC and the film suface, unidirectional alignment of the LC is unduced. A thin film of poly(vinyl cinnamate) (PVCi), one of the representative photo-crosslinkable photoresists has attracted special attention owing to the high photo-reactivity of the cinnamate group which porvides a photo-active surface for achieving the photo-control of in-plane alignment of the LC with polarized UV irradiation. However, an insufficient thermal stability of the photo-induced LC alignment on PVCi layer is a major hindrance to further progress in developing liquid crystal displays(LCDs). In this work, a new cinnamate-terminated imide oligomers was prepared and used as an alignment layer for the photo-induced LC alignment. The introduction of the imide segment in the main chain was aimed at providing thermal stability.