Solute diffusion in hydrated polymer networks. Part 1.—Cellulose gels

Abstract

Translational diffusion measurements on different homologous series (n-alcohols, polyhydric alcohols, oligosaccharides and alkali metal chlorides) and polyethylene oxide polymers in a densely crosslinked water-swollen cellulose gel (83 % water) are described. Solute diffusion coefficients in the gel phase are considerably lower than for free diffusion. The range of diffusion coefficients was 3.6 × 10^–6 to 0.12 × 10^–6 with corresponding ratios to free diffusion values 0.235 to 0.09. It is shown that the effect of the polymer matrix is a constant factor for the smaller molecules and that the reduction is due to a network-induced increase in the local viscosity of the medium. Only at high molecular weight does an increased collision frequency of the solute with polymer segments result in additional reduction of diffusion coefficients.