Mechanism of poly(N-isopropylacrylamide) cononsolvency in aqueous methanol solutions explored via oxygen K-edge X-ray absorption spectroscopy

The cononsolvency mechanism of poly(N-isopropylacrylamide) (PNIPAM), dissolving in pure methanol (MeOH) and water (H2O) but being insoluble in MeOH-H2O mixtures, was investigated by O K-edge X-ray absorption spectroscopy (XAS). The cononsolvency emerges from the aggregation of PNIPAM with MeOH clusters, leading to the collapse of the hydrophobic hydration of PNIPAM.