Generation of pretilt angle for nematic liquid crystal using the photodimerization method on various new photo-crosslinkable polyimide based polymers

We synthesized the various new photo-crosslinkable polyimide based polymers and generation of pretilt angle for a nematic liquid crystal (NLC) using a photodimerization method on the photopolymers was studied. A good thermal stability of the photopolymers was measured by thermogravimatric analysis ( TGA) measurement until 450 degreesC. The NLC pretilt angle generated was ab out 2.5 degrees -3.0 degrees by polarized UV exposure on the photopolymers containing a biphenyl (BP), decyl (De), and cholesteryl(chol), chalcone(Cha l) group, respectively. However, low pretilt angle of the NLC was measured by polarized UV exposure on the photopolymers containing the fluorine and c halcone group. The NLC pretilt angle generated is attributed to the bipheny l and alkyl moieties, and the photo-dimerized chalcone group of the photopo lymer.