Designing melt flow of poly(isobutylene)-based ionic liquids

A series of novel poly(isobutylene)-based stable ionic liquids (PIB-ILs) with strongly temperature dependent nano- and mesostructures is reported. The molecular design relies on the use of a liquid polymer with an ionic liquid-head-group, introducing liquid properties by both the polymeric chain as well as the ionic liquid (IL) head-group thus enabling terminal flow in a range which cannot be addressed with classical ILs with respect to the design of potential self-healing materials. Modifying both the anchored cation and anion as well as the molecular weight of the attached polymer chain, the nanostructure and the viscoelastic behavior of PIB-ILs can be engineered. Detailed small-angle X-ray scattering (SAXS) investigations as well as rheology studies have been conducted to reveal structure, viscoelastic properties and relaxation behavior of the prepared PIB-ILs. All investigated PIB-ILs exhibited a defined nano- and mesoscale ordering at room temperature, whereas the nature of the anchored cation showed a strong impact on the temperature-dependence of the mesoscale-structure as well as on the flow behavior of PIB-ILs. Exchange of the bromide anion to bis(trifluoromethylsulfonyl)imide led to the loosening of the observed clusters and to lattice disorder-order transitions (LDOT) at lower temperatures, leading also to terminal flow at lower temperatures. Investigated PIB-ILs exhibited short relaxation times and the reestablishment of the nano/mesoscale morphology immediately after cooling at room temperature, which makes them suitable for the engineering of novel self-healing materials.