Birefringent Pattern Formation in Photoinactive Liquid Crystalline Polymer Films Based on a Photoalignment Technique with Top-Coating of Cinnamic Acid Derivatives via H-Bonds.

Abstract

The application of a top-coating of 4-methoxy cinnamic acid (MCA) onto a photoinactive liquid crystalline polymeric film containing benzoic acid (BA) side groups (P6BAM) is shown to enable thermally stimulated, photoinduced reorientation of the polymer structure. Annealing the MCA-coated P6BAM films leads to H-bond formation between BA and MCA, which also effectively smooths the film surface. Exposure to linearly polarized (LP) UV light initiates axis-selective photoreaction of the MCA groups; subsequent thermal treatment in the LC temperature range of P6BAM amplifies molecular reorientation of the BA side groups, while simultaneously eliminating the MCA molecules. Selective inkjet coating of MCA provides a facile route for the fabrication of patterned, oriented, and rewritable P6BAM films with multiple controlled alignment directions.