Aggregation of pyrene in poly(alkyl methacrylate) films revealed by time-resolved total internal reflection fluorescence spectroscopy

Abstract

Fluorescence spectra and decay curves of pyrene in poly(alkyl methacrylate) (methyl, n-propyl, isobutyl and cyclohexyl) films cast on sapphire substrates were measured under total internal reflection and normal excitation conditions, and were compared with each other. On the basis of the intensity ratio of the excimer to the monomer fluorescence and the fluorescence decay curve under the normal condition, the degree of pyrene aggregation in these films is discussed in terms of the solubility parameter, chain flexibility and hydrophobicity of the host polymers. Both the difference in the degree of pyrene aggregation and the difference in micropolarity around pyrene molecules between the vicinity of the sapphire/polymer interface and the bulk were found to be quite common for these polymer films cast on sapphire plates, and are discussed in terms of the interaction between substrate surface and polymers. The effect of tacticity of poly(methyl methacrylate) on the degree of the pyrene aggregation and the effect of labelling with pyrene were also investigated.