Molecular size effects of diarylnitrone additive on the refractive-index change in poly(methyl methacrylate) film

Through a UV spectral analysis of the photorearrangement reactions in hydroxy- and methoxy-substituted diarylnitrones, it was found that the maximum wavelength of the first absorption band in these nitrone derivatives solubilized into poly(methyl methacrylate) film can be used as a measure of the refractive-index change which is directly related to the change in linear polarizability. It was also found that steric bulkiness of the alkyl substituent attached at the para-position on the N-aryl benzene ring contributes to the magnitude of refractive-index change to only a negligible extent.