Polymer Modification via Vapor Phase Infiltration for Chemically and Mechanically Resilient Membranes

Abstract

In recent years, membrane separations have been widely applied in wastewater treatment and gas separations due to their low energy requirements. Compared to ceramic membranes, which are highly stable but costly to manufacture, polymeric membranes have the greatest market share because of their low cost and scalable production. However, many of these polymers are unstable in organic solvents and at high temperatures, which has limited their use in applications requiring harsh conditions, such as organic solvent nanofiltration. An alternative class of membrane materials is inorganic-organic hybrid composite membranes, which exhibit enhanced stability compared to their additive-free polymers. In this work, we explored the modification of polymeric membranes with vapor phase infiltration (VPI), a post-synthetic modification technique that uses reactive vapors to enhance key polymer properties by incorporating inorganic or hybrid components. First, we studied the economic feasibility of membrane modification via VPI, estimating the cost of the VPI process based on similar techniques used in industry. We then investigated the influence of metal oxide infiltration on the chemical stability and mechanical properties of a common membrane support material, polyethersulfone, showing that infiltration depth and loading of composite strongly affect membrane stiffness and resilience. To mitigate the measured loss of ductility caused by metal oxide incorporation, alternative VPI chemistries such as metal alkoxides were explored, demonstrating successful integration of organic reactants into polymers. Finally, to accelerate development and optimization of new vapor phase processes, a high-throughput multiplexing reactor design was developed. Overall, these studies demonstrate the versatility of VPI as a cost-effective approach for tailoring polymeric membranes.