Influence of molecular structure on anisotropic photoinduced decomposition of polyimide molecules

Abstract

We have investigated the anisotropic decomposition of polyimide molecules induced by irradiation of linearly polarized ultraviolet light (LPUVL). Three polyimides were examined: poly [4,4′-oxydiphenylene-pyromellitimide], poly [4,4′-oxydiphenylene-1,2,3,4-butanetetracarboximide] and poly [4,4′-oxydiphenylene-1,2,3,4-cyclobutanetetracarboximide] (CBDA-ODA). Anisotropic decomposition was monitored by measuring the polarized infrared absorption spectra of ∼10 nm thick films as a function of LPUVL exposure. Among the three polyimides, CBDA-ODA showed the largest anisotropy of decomposition in the initial stage of LPUVL exposure. This result suggests that CBDA-ODA is a suitable polyimide material for photoinduced liquid crystal alignment based on photodecomposition reactions. The details of the LPUVL exposure dependence of the film anisotropy are discussed.