The Influence of Water on Choline-Based Ionic Liquids

Choline and geranic acid (CAGE)-based ionic liquids have been recently developed for applications in drug delivery. Understanding the microscopic structures of CAGE in the presence of water is critical for its continued use in biomedical applications as it will undoubtedly come into contact with water in physiological fluids. Water can drastically impact the physicochemical properties of the ionic liquids, including CAGE. Computational and experimental characterization, namely viscosity, conductivity, and self-diffusion coefficient, were employed here to understand the properties of equimolar CAGE (1:1 choline/geranic acid) in the presence of varying amounts of water. It was found that under stored conditions, 1:1 CAGE contained up to 0.20 mole fraction water. Experimental and computational studies indicate that microscopic intraionic interactions within CAGE are not substantially changed until the water content exceeds 0.65 mole fraction. At this point, we theorize that the geranate ions undergo reorgani...