Hierarchically Nanostructured Polyisobutylene-Based Ionic Liquids

A new type of highly temperature stable ionic liquid (IL) with strongly temperature dependent nanostructures is reported. The molecular design relies on the use of a liquid polymer with an ionic liquid headgroup, introducing liquid properties by both the polymeric and the ionic liquid (IL) headgroup. The IL polymers (poly­(isobutylene)­s) <b>3a</b>–<b>3c</b> (PIB-ILs) were prepared by a combination of living carbocationic polymerization (LCCP) and subsequent “click” chemistry for attachment of methylimidazolium (<b>3a</b>), pyrrolidinium (<b>3b</b>), and triethylammonium cations (<b>3c</b>). All three investigated PIB-ILs exhibited pronounced nanostructural organization at room temperature depending strongly on the nature of the anchored cation. Whereas the morphology of the imidazolium-based PIB-IL <b>3a</b> shows high thermal stability up to the decomposition temperature, order–order (OOT) and lattice disorder–order transitions (LDOT) characteristic for common ionomers could be observed in the case of pyrrolidinium <b>3b</b> and ammonium-based <b>3c</b> PIB-ILs. Control of flow behavior as well as adjustable relaxation times from the liquid to the viscoelastic regime can be adjusted by choice of the appropriate IL headgroup