Water diffusion at short times in hydrophilic polymer studied by an ion beam analysis technique

Gravimetric measurements establishing D ₂O as a good model for H ₂O diffusion in a hydrophilic polymer are reported. An MeV ³He ion microbeam technique is described which enables the measurement of the diffusion coefficient for initial Fickian diffusion of deuterated water into hydrophilic polymer. A raster scanned microbeam is used to bombard a sample cooled by liquid nitrogen. Spectra from ³He interactions with both 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 coefficient is deduced for initial water diffusion into tetrahydrofurfylmethacrylate/Poly(ethylmethacrylate) (THFM/PEM) at 37°C.