Photophysical studies of polymers

Abstract

One means of stabilising a polymer against irradiation involves energy transfer between a fluorescent polymer (donor) and a photostabiliser (acceptor) which removes some of the absorbed energy from the polymer. Polymers examined for this purpose were mainly conjugated derivatives of polystyrene and poly(vinylchloride). The dependence of donor emission on concentration of acceptor has been used to evaluate a transfer distance from donor to acceptor in fluid and rigid media. Polarisation measurements on thin films demonstrate that transfer is a long-range intermolecular process with no down chain migration of energy prior to transfer. Rotational Brownian motion in styrene copolymers has been studied in solution by fluorescence quenching and polarisation to determine relaxation times for the emitting species. Variable temperature work on fluorescence has highlighted the effect of chain mobility on emission spectra while a novel method for measuring diffusion coefficients has been proposed. Photodegradation of thin polymer films has been followed under accelerated weathering conditions using a medium pressure arc with a pyrex filter. The results reveal a subtle correlation between structure and reactivity. As an extension, polymer and acceptor have been simultaneously irradiated to examine the stabilising effect of the acceptor.