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

Abstract

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 the improvement of the performances of these materials used in a wide range of applications. The present work aims to take advantage 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, IL vinyl monomers and crosslinkers were polymerized in the presence of non-polymerizable ILs within the outer phase of a CO₂-in-IL high internal phase emulsion (HIPE). Specific macromolecular surfactants were synthesized using controlled radical polymerization techniques and tested for the stabilization of the CO₂-in-IL 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 provided 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 a simple anion exchange reaction.