Effect of chemical structures of polyimides on photosensitivity of liquid crystal alignment using a polarized UV exposure

Unidirectional liquid crystal (LC) alignment produced by polarized UV expos ure was examined using polyimides (PIs) synthesized using different diamine s. The dichroic ratio of the resulting LC cells suggests that the UV photos ensitivity is primarily controlled by the chemical structures of the PIs us ed. The UV absorption and fluorescence spectra of the PI films, and molecul ar conformations of the diamines, indicate that the photosensitivity is con trolled by the UV absorption efficiencies and molecular conformations of th e PIs.