Light induced cis–trans isomerization of azo compounds in polymethyl methacrylate Original Research Article

UV–VIS spectroscopy has been used to monitor the kinetics of cis→trans isomerization of two azo compounds following trans→cis photoisomerization that was carried out under light with shorter (405 nm) and longer (546 nm) wavelengths in polymethyl methacrylate. Light with shorter wavelength produces more reactive cis particles. The results are explained in terms of the following model. First, some fraction of trans molecules does not isomerize into cis molecules under longer wavelength irradiation in polymethyl methacrylate but does so for shorter wavelength. Second, these molecules have a greater rate constant of “dark isomerization” and a greater quantum yield of back photoisomerization under 546 nm irradiation.