Macroporous poly(ionic liquid)/ionic liquid gels via CO2-based emulsion-templating polymerization

Structuring poly(ionic liquid)s (PILs) into porous materials or swelling PILs with free ionic liquids (ILs) has received specific attention recently and contributed to improve the performances of these materials used in a wide range of applications. The present work aims to take benefit of both approaches and produce macroporous PIL/IL gels in a single step through an innovative emulsion-templated polymerization method based on supercritical carbon dioxide (scCO2). More precisely, ILs vinyl monomers and crosslinkers were polymerized in the presence of non polymerizable ILs within the outer phase of a CO2-in-ILs high internal phase emulsion (HIPE). Specific macromolecular surfactants were synthesized by controlled radical polymerization techniques and tested for the stabilization of the CO2-in-ILs emulsions. While optimizing the polymerization conditions, we found that adding a limited amount of water in the medium was beneficial for the emulsion stability. Overall, this straightforward process gave access to macroporous polyHIPEs composed of poly(vinyl imidazolium) networks swollen by ‘free’ vinyl imidazolium-based ILs having interesting properties such as switchable polarity upon simple anion exchange reaction.