(410c) Engineering and Modeling Ion Transport in Sulfonated Polysulfone

Providing sustainable supplies of purified water and energy is a critical global challenge for the future, and polymer membranes will play a key role in addressing these clear and pressing global needs for water and energy. Polymer membrane-based processes dominate the desalination market because they are more energy efficient than thermal desalination processes, and polymer membranes are crucial components in several rapidly developing power generation and energy storage applications that rely on membranes to control, selectively, rates of ion transport. Much remains unknown about the influence of polymer structure on basic intrinsic transport properties, and these relationships are important for designing next generation polymer membrane materials.

Key to controlling ion transport in membranes for water purification and energy applications is engineering interactions between ions and the solvated polymer matrix. This presentation presents ion sorption and diffusion properties of sulfonated polysulfones containing biphenol and hydroquinone linkages. Microwave dielectric relaxation spectroscopy, a tool that enables study of hydrated polymer membranes because water molecule dipoles can be probed in the microwave frequency region, was used to provide unique insight into dielectric permittivity (or dielectric constant) properties. This information was used to aid modelling of ion sorption properties, and a combination of the dielectric and Donnan-Manning ion exclusion was required to effectively model ion sorption in sulfonated polysulfone. Additionally, ion diffusion in sulfonated polysulfone was characterized as a function of salt concentration to probe and explain the origins of salt diffusion coefficients that increase with increasing salt concentration in contrast to observations made on other charged polymers. This presentation discusses structure-property relationships, resulting from both experimental characterization and modeling efforts, for sulfonated polysulfone to advance fundamental understanding of the ion transport properties that govern ion transport in polymeric materials considered for desalination and electric potential field-driven membrane applications to help address global needs for clean water and energy.