Optical control of alignment and patterning in an azobenzene liquid crystal photoresist

Abstract

This report describes a liquid crystalline material that can be cured and patterned with green light and photoaligned with blue light. The liquid crystalline material consists of azobenzene repeat units that undergo photoisomerization between trans and cis isomers when irradiated with UV and visible light. A formulation containing an azobenzene diacrylate mesogen was spin-coated and cured with green light through a photomask to generate a patterned film. Unexposed regions of the film were rinsed away. Exposure of the pattern to UV light to generate a cis enriched film greatly enhances the film's propensity to photoalign when exposed to polarized blue light. The orientations of the mesogenic repeat units are characterized with polarized UV-Vis spectroscopy and birefringence measurements. Photochemical switching between cis and trans conformations of the azobenzene chromophore is characterized with UV-Vis spectroscopy.