Dynamics of water sorbed in reverse osmosis polyamide membrane

Dynamical motion of water sorbed in reverse osmosis polyamide membrane (ROPM) material is reported as studied by quasielastic neutron scattering (QENS) technique. The ROPM studied here has pore size of 4.4 Å as determined by positron annihilation lifetime spectroscopy. Analysis of the QENS data showed that diffusion behavior of the water within the membrane is describable by random jump diffusion model. A much longer residence time is found as compared to bulk water. Positive shift of the freezing point as observed in differential scanning calorimetry indicates presence of strong attractive interaction corroborating the slower diffusivity as observed in QENS.