Synthesis of a polyoxadiazole containing the 4-hydroxypyridine group and photo-induced fluorescent imaging on the polymer film

A polyoxadiazole containing the 4-hydroxypyridine group, introduced to enhance the intermolecular interaction between polymer chains as well as for photosensitization, was synthesized from a corresponding precursor polyhydrazide. The absorption and emission spectra of the polymer film exhibited red-shifted maxima compared to those of the polyoxadiazole in chloroform solution, indicative of the presence of significant intermolecular interactions. The synthesized polymer showed a unique fluorescence enhancement upon UV irradiation in solution as well as in the film, presumably due to the photosensitized oxidation of hydroxypyridine groups to produce pyridone structures having different intermolecular interactions. Thus, this phenomenon enabled us to obtain a stable patterned image with enhanced fluorescence intensity in the UV-exposed area of the polymer film without any subsequent processes such as baking or etching.