Diffusion of polystyrene in solution studied by photon correlation spectroscopy

Abstract

The diffusion behaviour in toluene, and in some cases toluene + cyclohexane mixtures, of three polystyrenes, two of narrow molecular weight distribution and one of broad molecular weight distribution, has been studied using photon correlation spectroscopy. The apparent diffusion coefficient D increases with increasing concentration in all cases. For a narrow molecular weight sample the correlation function g⁽¹⁾(K, τ) shows a marked departure from a single exponential decay as the concentration increases, and the possible causes of this behaviour are considered in terms of the theory of the light scattering process. The variation of D with concentration and with molecular weight is examined.