Specific solubility behavior of quaternary ammonium-based poly(ionic liquid) particles by changing counter anion

The solubility behavior of poly(ionic liquid) (PIL) particles, which were prepared by dispersion polymerization of ([2-(methacryloyloxy)ethyl]trimethylammonium bis(trifluoromethanesulfonyl)amide), [MTMA][TFSA], was observed in detail. The solubility of PILs was varied by changing the counter anion. A PIL with [TFSA] anion does not dissolve in polar solvents such as ethanol; however, a PIL with Br anions does dissolve in ethanol. Upon the addition of LiBr to ethanol solution at high concentrations (>2.5 wt.%), the PIL particles dissolved from their outer surface and the counter anions [TFSA] were replaced with Br anions on the particle surfaces. On the other hand, in the case of the ethanol solutions at low LiBr concentrations (<2.5 wt.%), a specific solubility behavior was observed: domains inside the PIL particles were generated before their dissolution, most likely due to osmotic pressure. Moreover, PIL particles having hollow structures were prepared using this specific solubility behavior. (C) 2013 Elsevier Inc. All rights reserved.