Hierarchically Nanostructured Polyisobutylene-Based Ionic Liquids

Abstract

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) 3a–3c (PIB-ILs) were prepared by a combination of living carbocationic polymerization (LCCP) and subsequent “click” chemistry for attachment of methylimidazolium (3a), pyrrolidinium (3b), and triethylammonium cations (3c). 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 3a 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 3b and ammonium-based 3c 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.