Photoaging of methyl methacrylate-methacrylic acid copolymer doped by laser dyes and diphenylthiourea

For methyl methacrylate-methacrylic acid copolymer colored by laser dyes (R hodamine 6G and Coumarin 7), the mutual effect of polymeric matrix and dyes on the kinetics of their photochemical aging was studied. Diphenylthiourea was introduced into the copolymer as a modifying additive. It was establis hed that, upon irradiation with a mercury lamp, both the dyes and diphenylt hiourea exert photostabilizing effects on the copolymer. It was found that there exists a correlation between the photofading of the dyes and the proc esses related to the photoaging of the copolymer, such as the degradation o f macrochains, the accumulation of free radicals, and a reduction in the tr ansmission coefficient. Introduction of diphenylthiourea causes a tenfold i ncrease in the generation photostability of the copolymer samples colored b y Rhodamine 6G, and consequently, their operating life as the laser-active elements.