Grayscale Photopatterning of an Amorphous Polymer Thin Film Prepared by Photopolymerization of a Bisanthracene-Functionalized Liquid-Crystalline Monomer

A method for grayscale photopatterning of an amorphous polymer film derived from a bisanthracene-functionalized liquid-crystalline monomer is developed. Solution photopolymerization of a monomer with two anthracene moieties, one at each end, affords an amorphous polymer. A combination of irradiation with patterned UV light and heating results in photopatterning on thin films prepared from the polymer. On non-irradiated areas of the film, the polymer reverts to the monomer owing to the thermal back-reaction of the anthracene photodimer, forming an ordered phase. On irradiated areas remaining in the amorphous phase, the thermal back-reaction is suppressed. This phenomenon results in a clear contrast and visual images on the film under polarized light. Grayscale photopatterning is also made possible for the solution-polymerized polymer by controlling the intensity of exposure. In addition, rewritable photopatterning can be achieved by melt photopolymerization of the monomer. The new photopatterning is essentially nondestructive because it needs neither image development nor anthracene-excitation light for reading.