WATER DIFFUSION AT SHORT TIMES IN HYDROPHILIC POLYMER STUDIED BY AN ION-BEAM ANALYSIS TECHNIQUE

Gravimetric measurements establishing D2O as a good model for H2O diff usion in a hydrophilic polymer are reported. An MeV He-3 ion microbeam technique is described which enables the measurement of the diffusion coefficient for initial Fickian diffusion of deuterated water into hy drophilic polymer. A raster scanned microbeam is used to bombard a sam ple cooled by liquid nitrogen. Spectra from He-3 interactions with bot h deuterium and carbon in the polymer matrix are collected. The latter is used to normalise water concentrations resulting from exposure of the polymer to heavy water for different times. A diffusion coefficien t is deduced for initial water diffusion into trahydrofurfylmethacryla te/Poly(ethylmethacrylate) (THFM/PEM) at 37 degrees C.