Dielectric study of concentration fluctuations in concentrated polymer solutions

Dielectric relaxation of the segmental mode in concentrated solutions of poly(vinyl acetate) (PVAc) in toluene (Tol) and in 1-methylnaphthalene (MN) and those of poly(vinyl octanoate) (PVOc) in Tol were studied. It was found that the distributions of relaxation times in concentrated solutions were much broader than those in dilute solution and in the undiluted bulk polymer. The broad spectra were ascribed to local heterogeneities. The half width Lambda increased with decreasing temperature and this behavior was explained by assuming that Lambda is proportional to the amplitude of the loctaual concentration fluctuation Deltaphi times the slope of the phi dependence curve of the average relaxation time . This assumption leads to a linear relationship between A and Deltaphi/(T - T-0)(2) where T-0 is the Vogel critical temperature. Using this relation, we attempted to estimate Deltaphi. (C) 2002 Elsevier Science B.V. All rights reserved.