New approach to probing polymer and polymer blend structure using electronic excitation transport

Abstract

A theoretical study of electronic excitation transport in polymer systems is presented. GYt), the time-dependent ensemble-averaged probability that the excitation is on the originally excited chromophore, is calculated by using an approach involving a density expansion. It is shown that this quantity is a direct observable in a time-resolved fluorescence depolarization experiment. The effects of the finite volume associated with a single polymer coil or a small aggregate in a polymer blend are considered explicitly. Calculations are presented for systems having a Gaussian ensemble-average segmental distribution. The influences of density, volume, and aggregation are illustrated. Gg(t) can yield reliable information about the local chromophore distribution of systems for which a lack of knowledge of the number of excimer traps prevents quantitative application of trapping experiments. The approach described here should be particularly valuable in obtaining structural information about very low concentration guest polymers in polymer blends and solutions.