Phototransformation of merocyanine forms of spiropyrans in amorphous polymeric media

Abstract The influence of annealing time below T g on the kinetic behaviour of photochromic spiropyran molecules, with long aliphatic substituents, embedded in polystyrene solid solution is discussed. The data indicate an increase of Mc → Sp phototransformation rate as a function of aging, in contrast to the results of the influence of free volume distribution in the polymers obtained by using azobenzene chromophore. A linear dichroism spectrum produced by photoselection and phototransformation kinetics measured at different parts of the Mc absorption band reveal that the observed divergences may result from different kinetic constants of individual stereoisomers and from the presence of long chain substituents in the probe under study.