(463e) Water and Salt Transport in Polymer Membranes Prepared By Solvent-Free Melt Processing

In industry today, polymer membranes are formed via solution processing (i.e., phase inversion techniques) that require large amounts of hazardous organic solvents. While effective from a processing standpoint, these membrane formation methods are highly material-specific and present challenges in controlling pore architecture (i.e., pore size, shape and distribution), which enormously affects the transport of small molecules and ions through the resultant membrane. Moreover, by avoiding the use of toxic and hazardous solvents for membrane formation, many benefits could be realized in terms of cost and environmental impact, and advancements in processing could also provide further insight on the next generation of membrane materials. Herein, work is presented on a new method of membrane formation using charged polymers on porous thin supports via a state-of-the-art multi-nanolayered technology, mainly aimed at producing membranes for desalination and water purification.

Robust, ion-exchange membranes based on sulfonated polymers were prepared by solvent-free melt processing, providing the first example of melt-processed membranes for applications in desalination. To investigate the polymer physics underlying the effects of processing history on these systems, transport of small molecules and ions has been investigated.

Interestingly, melt processed membranes (sulfonated polysulfone, BPS) prepared by different routes (i.e., plasticizer composition, processing temperature, and post-processing treatment) show different water and salt transport properties, compared to solution processed membranes. To understand the origin of this difference, ¹H NMR analysis and FT-IR analysis were conducted, but no chemical change was detected. Rather, differences in mass transport behavior result from processing methods having a significant effect on the polymer structures. These results imply that, in addition to varying the chemical structure of the polymer, varying processing methods also provides extra freedom to modify polymer properties.