title: Enhanced self-assembly for the solubilization of cholesterol in molecular solvent/ionic liquid mixtures.
abstract: The development of new solvents combining greatly enhanced solubility for sparingly soluble compounds and good kinetic properties is challenging. In this study, we constructed a family of new molecular solvent/ionic liquid (IL) mixtures with amphiphilic, anionic functional long-chain carboxylate ionic liquids (LCC-ILs) as a key component for the solubilization of sparingly soluble compounds, using cholesterol as a model solute. Polarized optical microscopy (POM), wide angle X-ray diffraction (WAXD), Fourier-transform infrared (FTIR) spectra and1H NMR showed that ordered mesoscopic structures, such as liquid crystals (LCs), were formed when cholesterol was dissolved in the mixtures, presenting a self-assembly induced dissolution mechanism driven by H-bond interaction and van der Waals forces in the mixtures. A synergistic effect between the molecular solvents and LCC-ILs was revealed, which contributed to enhanced solute-solvent self-assembly in dissolution over pure LCC-ILs and thus elevated solubility. Additionally, the effect of IL concentration, solvent type and anionic alkyl-chain length on self-assembly and solubility was investigated. These mixtures showed unparalleled solubilities for cholesterol, while maintaining a low viscosity. The quantitative solubilities (g g-1) of cholesterol were as high as 0.70, 0.84 and 0.82, respectively, at 25 °C in ethyl acetate/[P4444][C15H31COO] (50 wt%), n-heptane/[P4444][C15H31COO] (40 wt%) and ethyl acetate/[P4444][C17H35COO] (50 wt%) mixtures, which were the highest solubilities of cholesterol ever reported, six- to 980-fold higher than traditional molecular solvents and even one- to seven-fold higher compared to pure LCC-ILs. These results demonstrated the considerable potential of molecular solvent/LCC-ILs mixtures as promising solvents for solubilization and advanced separation processes.
authors.affiliation: Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China. yangqw@zju.edu.cn.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Jin
authors.forename: Yuqi
authors.initials: Y
authors.lastname: Ke
authors.forename: Xianxian
authors.initials: X
authors.lastname: Liu
authors.forename: Qiwei
authors.initials: Q
authors.lastname: Yang
authors.forename: Zongbi
authors.initials: Z
authors.lastname: Bao
authors.forename: Baogen
authors.initials: B
authors.lastname: Su
authors.forename: Qilong
authors.initials: Q
authors.lastname: Ren
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Yang
authors.forename: Huabin
authors.initials: H
authors.lastname: Xing