Kinetic matrix effects (response and density distribution functions): ring closure. Reaction of indolinobenzospiropyrans in glassy poly(alkyl methacrylates)

Abstract

The ring closure (bleaching) reaction of photochromic indolinobenzospirans is a fast unimolecular process with a finite activation volume. When the reagent is immobilised in a rigid matrix, the isomerization is controlled by the amount of free volume in the neighbourhood of the reacting molecule and so the distribution of reaction rates reflects the density distribution in the matrix. The theory of such kinetic matrix effects is presented and methods of evaluating the reagent response and matrix density distribution functions are discussed. Ring closure reactions of three such compounds in four polymeric matrices are reported and the complete functions evaluated for 8-bromo-2′,2′-dimethyl-6-nitro-1′-phenyl-(2H-[1]benzospiropyran-2,2′indoline) in poly(methyl methacrylate).