Nanostructure in amino acid ionic molecular hybrid solvents

Choline amino acid ionic liquids ([Ch][AA]ILs) have shown outstanding capacity for extraction and biomass pre-treatment but their very high viscosity renders them difficult to handle and inhibits their large-scale application. As a result, [Ch][AA]ILs are commonly mixed with a low-viscosity molecular solvent such as water to form hybrid solvents, which preserves the favourable characteristics of ILs while enhancing physical properties. Here we investigate the structure of binary mixtures of choline lysinate and phenylalaninate with water and primary alcohols. Contrast-variation neutron diffraction and computational modelling shows the nanostructure of both [Ch][AA]ILs can be engineered by mixing with alcohols up to high concentrations, and that the abundance of hydrogen-bond donors is a critical determinant of the overall liquid structure. This provides a new strategy to engineer and fine tune solvent nanostructure for the design of application-specific, biofriendly hybrid solvent systems.