Self-diffusion of THO within tactic poly(2-hydroxyethyl methacrylate) membranes

Abstract

The self-diffusion experiment of water was performed across two series of tactic poly(2-hydroxyethyl methacrylate), P(HEMA) membranes, prepared by crosslinking with various amount of hexamethylene diisocyanate (HMDIC). The tagging material was tritium hydroxide (THO) and the efflux of THO was counted on a Liquid Scintillation Counter. The transport data of THO show that the permeability decreases as the amount of HMDIC increased from 2.5 to 10 mole% and self-diffusion coefficient shows a parallel trend with it. The diffusivity data was compared with the free diffusion data of ordinary water and discussed in terms of the change of water structural orderliness within membranes. Using the relation between viscosity and diffusivity derived from Eyring``s absolute rate theory, the corresponding viscosities of water within two series of tactic P(HEMA) membranes were obtained. From this, it is seen that the viscosities of water within tactic P(HEMA) membranes may have the same values with those of supercooling water whose temperature ranges from -28℃ to -36℃.