(396g) Influence of Polymer Backbone Rigidity on the Water and Ion Transport Properties of Low Water Content Membrane Polymers
Global need for sustainable water and energy sources presents an opportunity for polymer science as many technologies for water purification and some emerging power generation technologies rely on polymeric membranes to control rates of water and ion transport. For polymers that are of interest for membrane applications, the water/salt selectivity is a critical property that describes the intrinsic ability of the polymer to transport water as opposed to salt. Traditionally, transport of water and salt through hydrated polymers has been described in terms of sorption and diffusion via the solution-diffusion model. An observed tradeoff relationship between water/salt permeability selectivity and water permeability, constructed based on transport data for several different polymers, suggests that both sorption and diffusion selectivity values contribute significantly to water/salt permeability selectivity. To separate the influences of sorption and diffusion selectivity on water and salt transport, we prepared chemically similar polymers that have different segmental dynamics. At equivalent water content, polymers with slower segmental dynamics are more diffusion selective than those polymers with more rapid segmental dynamics. The results of this study provide fundamental structure-property insight into water and salt transport in hydrated polymers.