Diffusion and association of water in some polyalkylmethacrylates. Part 2.—Transient state diffusion

Abstract

Sorption-rate curves were determined for water in polypropyl acrylate at 322 K and in polybutylmethacrylate at 313 K and analyzed to yield the concentration dependence of the diffusion coefficient. An earlier steady state analysis showed that the diffusion coefficient D decreased as the concentration C of sorbed water increased, consistent with clustering of the water in the polymer matrix. The transient and steady state diffusion coefficients are in good agreement, indicating that the process of clustering is rapid compared to that of diffusion. Procedures for obtaining the concentration dependence of D are examined in relation to systems for which D decreases with C. The method of Lin-Hwang is examined in detail.