Polymer membranes enable technologies that could address critical need for sustainable supplies of water and energy. Advanced membranes, however, are needed to realize fully the potential of these technologies. Much remains unknown about the chemical factors that influence polymer membrane transport properties, and understanding these fundamental structure-property relationships is critical for developing the next generation of polymer membranes. Transport in non-porous polymer membranes is often described by a solution-diffusion mechanism where both thermodynamic partitioning and diffusion contributions affect transport properties. In desalination membranes, polymers with simultaneously high water permeability and low salt permeability are desirable to prepare selective membranes that can efficiently desalinate water. Therefore, polymers that exclude salt are desirable. In electro-membrane processes, salt exclusion is also needed, as mobile salt (or co-ion) exclusion is critical for attaining favorable permselectivity properties that are critical for efficient operation of electromembrane processes. This study reports an investigation of the influence of polymer chemistry on salt exclusion in polymers for membrane applications. Microwave dielectric spectroscopy measurements were made on hydrated polymers based on poly(glycidyl methacrylate), pGMA. Relative permittivity properties are linked to ion sorption properties that are critical for desalination applications, but little is known about the influence of polymer chemistry and water sorption on relative permittivity. The pGMA-based materials considered in this study had lower relative permittivity compared to Nafion®, which is a perfluorosulfonic acid polymer considered for fuel cell applications, at comparable water content. This result favors ion exclusion and demonstrates the importance of polymer chemistry in engineering polymers for desalination membrane applications.

Influence of relative permittivity properties on ion transport in hydrated polymer membranes

2019 Spring National Meeting

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