Diffusion and association of water in some polyalkylmethacrylates. Part 1.—Equilibrium sorption and steady state permeation

The sorption, permeation and diffusion of water in a series of polyalkylmethacrylates has been studied for a number of temperatures in the range 298–353 K. In each case the diffusion coefficient decreased as the concentration of sorbed water was increased. The heat and the entropy of dilution decreased with concentration and the activation energy for diffusion increased. Polymethylmethacrylate was the exception in that both the heat of dilution and the activation energy for diffusion were independent of concentration. The results are consistent with significant clustering of the water molecules in the polymer matrix. A comparison is made with a random polycondensation model for the association of water through hydrogen-bond formation.