Interfacial characteristics of poly methyl methacrylate film aggregation of pyrene and micropolarity revealed by time-resolved total internal reflection fluorescence spectroscopy

Abstract

Fluorescence spectra and decay curves of pyrene in poly(methyl methacrylate) films, cast and spin-coated on sapphire substrates, were measured under a total internal reflection (TIR) and a normal excitation conditions and compared with each other. The difference in the intensity ratio of the first to the third vibronic bands of the pyrene monomer fluorescence was observed, which indicates that micropolarity around pyrene molecules in the vicinity of the sapphire/polymer interface is higher than that of the bulk. The intensity ratio of the excimer to the monomer fluorescence under the normal condition was larger than that under the TIR one. This result and the difference in the fluorescence decay curves under both optical conditions mean that an aggregate state of pyrene is different between the vicinity ofthe interface and the bulk. Similar phenomena were also observed for an air/polymer interface of the cast film. These interfacial characteristics of molecularly doped polymer films are discussed, and the formation process of these filmsis considered. © 1990 The Society of Polymer Science, Japan.