Radiation-Induced Coloration of Photochromic Dithienylethene Derivatives in Polymer Matrices

The high-energy radiation-induced coloration of photochromic dithienylethenes was studied in various polymer matrices with the aim of developing a reusable color plastic dosimeter. Upon γ-irradiation, polystyrene films containing 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene 1a and 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene 2a turned red and blue, respectively. The red and blue colors disappeared upon irradiation with visible light, and the films could be reused. In both films the absorption intensities of the colors increased linearly with the absorbed dose. Although radiation-induced coloration was clearly detected in polystyrene films, a color change was scarcely observed in poly(methyl methacrylate) (PMMA) and poly(N-vinyl carbazole) containing 1a and 2a. Excitation energy transfer from polymers to dithienylethenes is considered to play a role in the coloration process in polymer films.