(593c) Polystyrene-Terpineol Upper Critical Solution Temperature Tunability for Ultrafiltration Membrane Synthesis

One of the ways to fabricate membranes for different purification technologies is by temperature-induced phase separation (TIPS). Upper critical solution temperature (UCST) caused by intermolecular interactions in polymer-solvent system can be used in TIPS. At low temperatures, these interactions form polymer-rich and polymer-poor phases, which become the membrane matrix and pores, respectively. Limited research has been conducted on sustainable UCST-based membrane fabrication by trying to achieve phase-transition at lower temperatures. This study explored polystyrene terpineol blends' upper critical solution temperature (UCST) to synthesize membranes via the TIPS process. We investigated the impact of additives, including oleic acid (OL), gamma valerolactone (GVL), and limonene (LO), with varying hydrogen bonding on UCST and membrane formation. The cloud point temperature was determined visually and represented the temperature of the UCST. Scanning electron microscopy evaluated the pore size and shape of the synthesized membranes, while porosity was measured using the gravimetric method. Water flux and BSA rejection are also tested using a dead-end filtration mode. Our findings indicate that the additives' hydrogen bond propensity significantly impacts the UCST, with a change of over 35°C observed when varying the concentration of additives from 0-15 wt%. Furthermore, pure membranes and those containing 5 wt% of additives have a pore size of less than 50 nm, making them ideal for ultrafiltration membranes. Overall, our study offers a way to control UCST by adding small-molecule additives with varying hydrogen bond propensity and structure from it.