Hierarchically Mesostructured Polyisobutylene-Based Ionic Liquids.

The formation and design of a hierarchically nanostructured poly(isobutylene)-based ionic liquid (PIB-ILs) is reported, displaying assembly into classical multiplets and an additional ordering of the aromatic counteranions. Three PIB-ILs (M-n = 3600 and 8600 g mol(-1)), bearing imidazolium (1a), N-methylpyrrolidinium (1b), and triethylammonium cations (1c) together with the aromatic 2-(methylthio) benzoate anion are prepared via a combination of living carbocationic polymerization, "click" reactions and subsequent anion metathesis. The morphology of the novel PIB-ILs as well as its temperature-dependent behavior has been studied via small angle X-ray scattering, displaying two different transition temperatures: one originating from ordering of micelles within a cylinder, and the second from cylinder-cylinder arrangement. Furthermore, the incorporation of an aromatic, rigid, and bulky 2-(methylthio) benzoate anion into the PIB-ILs effects the formation of an internal assembly consisting of stacked cylindrical structures, composed from the mesoscale ordering of ionic "multiplets" characteristic for classical ionomers and from the typical distance of the cylinders themselves.