1C11 Alignment of polyamic acid molecules with azobenzene units in the main chain induced by UV light irradiation and by thermal imidization

Abstract

By using polarized infrared absorption spectroscopy, we have investigated the molecular alignment of thin films of polyamic acid (PAA) containing azobenzene units in the backbone structure. The molecular alignment was induced by irradiation of linearly polarized ultraviolet light (LPUVL). We found that the alignment of the PAA molecule through repeated photo-isomerization reactions of the azobenzene unit occurred with a low efficiency. When the LPUVL-irradiated PAA film was thermally imidized, we observed significant enhancement in the molecular order of the film. We found that the enhancement of molecular order plays an important role in the realization of polyimide films with large in-plane anisotropy.