(185a) Diffusion of Nanoconfined Ionic Liquid in Mesoporous Silica Microparticles

Ionic liquids (ILs) are versatile solvents for a multitude of applications, such as solubilization of recalcitrant biomass, catalysis, removal of aqueous waste products, and energy storage devices. Supporting ILs on a solid substrate or confining them within pores is one strategy to overcome the expense and unfavorable transport properties of bulk ionic liquids. The structures of ILs are changed in nanoconfinement relative to bulk systems due to interactions with the pore surface and pore size constraints. The resulting changes in thermophysical properties of confined ILs are hypothesized to affect the corresponding transport properties. Here we investigate the diffusivity a mobile dye in 1-Butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] confined within silica microparticles, as measured by the fluorescence recovery after photobleaching (FRAP) technique in confocal microscopy. Pore diameters (6.2 and 9.7 nm), dye hydrophobicity, and pore surface functionality are varied. Differential scanning calorimetry is used to confirm the confinement of the ionic liquid within the pores and presents further evidence of structural changes due to confinement. An understanding of the effect of nanoconfinement on transport in ILs is important to the design of potential applications using supported ILs, such as in membranes separations, electrochemical devices, and heterogeneous catalysis.