Synthesis and characterization of novel polyimides bearing a side chain composed of stilbene mesogen and undecyl spacer and the alignment ability of nematic liquid-crystal molecules

Abstract

Four different polyimides with side chains containing undecyl spacers and 4-fluorostilbene mesogen end groups were prepared, and their structures and the controllability of the liquid-crystal (LC) alignment with rubbing were investigated. From X-ray scattering and differential scanning calorimetry data, pyromellitic dianhydride (PMDA)-, benzophenone-3,3 ' ,4,4 ' -tetracarboxylic dianhydride (BTDA)-, and 4,4 ' -oxydi(phthalic anhydride) (ODPA)-based polyimides were shown to have layered structures and short-range ordering. Pretilt angles of LCs on the rubbed surfaces were 1-9 degrees, depending on the rubbing density and backbone. In particular, the long undecyl spacers caused the mesogenic stilbene end groups to lie next to the main chain, resulting in a reduction in the pretilt angles. (C) 2001 John Wiley & Sons, Inc.