Synthesis of novel aromatic polyimides containing bulky side chain for vertical alignment liquid crystals

In this study, a novel 4-(4-octyloxybenzoyloxy)biphenyl-3′,5′-diaminobenzoate and polyimides based on it were synthesized. The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for nematic liquid crystal (LC). The pretilt angles of LCs above 89° were kept after the rubbing process with 220 mm rubbing strength. The polyimide films as the alignment layer were baked at 120 °C for 12 h, the vertical alignment of LCs was still uniform and stable. Meanwhile, the UV–vis spectra of the novel polyimide films showed the high transparency in a visible wave length.