Mechanical Milling of Thermoresponsive Poly(N-Isopropylacrylamide) Hydrogel for Particle-Oriented Oil–Water Separation

The separation of oil and water is widely studied because of the promise of cleaning up oil spills. One pathway is with thermosensitive polymer-based hydrogels. As hydrogels are raised to the lower critical solution temperature (LCST), they undergo a change of state, from hydrophilic to hydrophobic. Oil–water separation using hydrogels in particle form that are responsive to external stimuli (e.g., magnetic field and temperature) are of great interest. This work uses a novel approach of ball milling dry hydrogel into different sizes and testing oil–water separation efficacy. This study investigated the potential for ball milling P(NIPAAm) bulk hydrogel into small particles size ranges (0–45, 45–90, 90–106, 106–150, and 150+ μm) and the resulting impact on oil–water separation. It was observed that the LCST for the p(NIPAAm) in gel form was 32 °C while increasing to ~40 °C for the powdered form. It was found that the hydrogel particles of different size ranges managed to capture 196, 207, 208, 162, and 124% of its weight in oil, respectively.