Poly(ionic liquid)s with superior swelling and enrichment properties in solvents

Abstract

A series of poly(ionic liquid)s (PILs) based on 1-vinyl-3-(3-sulfopropyl)imidazolium (VSpIm) and sodium p-styrenesulfonate (NaSS) have been successfully synthesized and fully characterized. The swelling behaviours of the PILs in 18 solvents with a wide range of Hansen solubility parameters (δ_T) were investigated. The PILs exhibited distinct swelling properties in solvents with δ_T > 24.5 MPa^1/2, such as water, formamide and methanol. The molar swelling ratio (Q_M), which represented the swelling ability of the PILs in solvent, was linearly positively correlated with the δ_T value. Moreover, the enrichment behaviours of the PILs in various mixed solvents were also studied. In water/solvent and formamide/solvent monophasic mixed solvents, the enrichment factors of the PILs to water and formamide were up to 39.82 (water/THF) and 17.69 (formamide/THF), respectively. The enrichment factor of the PILs to water (or formamide) was linearly positively correlated with the difference between δ_T (water) (or δ_T (formamide)) and δ_T (solvent). The excellent swelling and enrichment properties of the PILs in solvents were attributed to the strong interactions between the PILs and solvent molecules, especially the hydrogen-bonding interactions, which was supported by nuclear magnetic resonance (NMR) spectroscopy. Furthermore, a PIL was used as a catalyst for the hydration of alkyne and found that it had higher catalytic activity than those of both heterogeneous and homogeneous catalysts.