Tailored Diluent for Nanostructure and Viscosity Control in an Ionic Liquid

Ionic liquids (ILs) offer tunable physicochemical properties but are often limited by their high viscosities. This is commonly addressed by introducing low-viscosity diluents, which increase molecular complexity and frequently lead to nonlinear viscosity-composition relationships. Here, we designed a molecular diluent that mimics the parent IL. We demonstrate that this approach enables viscosity tuning over 3 orders of magnitude while preserving the self-assembled nanostructure of the neat IL across all compositions. This work establishes a new strategy for designing IL-diluent systems and provides a model platform to investigate the role of Coulombic interactions in governing the local structure and macroscopic properties.