(244a) Patterning Various Commercial Nanofiltration and Reverse Osmosis Membranes

There have been differing views on the ability to pattern polyamide thin-film composite (TFC) membranes directly by nano-imprint lithography. The goal of this study was to understand what factors control patternability, working towards a set of heuristics for use by the membrane community to pattern any polyamide TFC membrane. Despite completing a comprehensive set of experiments to investigate the roles played by membrane chemistry, surface properties, mechanical properties, and performance properties on pattern peak heights for thirteen commercial nanofiltration and reverse osmosis membranes, we found no correlation between the variables studied and patternability of individual membranes. We did discover significant differences in patternability between membranes grouped by polyamide class, with those prepared by interfacial polymerization of m-phenylenediame and trimesoyl chloride having the largest pattern peak heights. We further discovered that the humectant (pore filler) used for membrane preservation plays a role on the patternability of the membranes. Upon replacement of the original humectants used by the membrane manufacturers with a 15 wt% glycerol solution, the pattern peak heights approached a similar value for each membrane class. Tests performed to elucidate the role of the glycerol on patternability were inconclusive. Thus, while the humectant clearly contributes to membrane patternability, the reason why remains unknown.