Effect of concentration on the absorption and fluorescence spectra of pyrene in a solid solution of poly(methyl methacrylate)

Abstract

It is shown that the pyrene excimer fluorescence seen in poly(methyl methacrylate) at high concentrations does not arise from microcrystallites but from pairs of molecules close to the excimer configuration. The yield of this fluorescence is enhanced by aggregation. The aggregation is caused by an attraction between ground state molecules due to long range dispersion forces (van der Waals forces). These forces also account for an observed broadening and red shift in the absorption.