Surprisingly high, bulk liquid-like mobility of silica-confined ionic liquids

Abstract

Mesoporous silica monoliths were prepared by the sol-gel technique and filled with 1-ethyl-3-methyl imidazolium [Emim]-X (X=dicyanamide [N(CN)2], ethyl sulfate [EtSO4], thiocyanate [SCN], and triflate [TfO]) ionic liquids (ILs) using a methanol-IL exchange technique. The structure and behavior of the ILs inside the silica monoliths were studied using X-ray scattering, nitrogen sorption, IR spectroscopy, solid-state NMR, and thermal analysis. DSC finds shifts in both the glass transition temperature and melting points (where applicable) of the ILs. Glass transition and melting occur well below room temperature. There is thus no conflict with the NMR and IR data, which show that the ILs are as mobile at room temperature as the bulk (not confined) ILs. The very narrow line widths of the NMR spectra suggest that the ILs in our materials have the highest mobility reported for confined ILs so far. As a result, our data suggest that it is possible to generate IL/silica hybrid materials (ionogels) with bulk-like properties of the IL. This could be interesting for applications in, e.g., the solar cell or membrane fields.

Properties of Ionic Liquid Confined in Porous Silica Matrix

“…Functionalization [45] of silica matrix was also found to affect the phase behavior of confined IL. Gçbel et al [44] showed from DSC studies that in restrictive geometry, the melting point of [EMIM] based ILs decreases by~8 to 148C. Further, they found a shift in NMR peaks of bulk IL on confinement in pores.…”

“…The confinement of many ILs has been found to result in changes in the thermal properties (like melting point) as studied by differential scanning calorimetry (DSC). [41][42][43] Recently, Gçbel et al [44] have studied the DSC, NMR and IR spectra obtained from inserting 4 ] etc) in silica of different pore sizes, which was achieved by varying base catalysts like pyridine, 3-fluoropyridine and 2-picoline. More recently Gçbel et al [45] obtained IL-silica monoliths of different pore sizes by functionalizing the silica pore walls by adding N,N-dimethyl-pyridine-4-yl-(3-triethoxysilylpropyl)-ammonium iodide and 3-fluoropyridine and 2-(4-pyridylethyl)triethoxysilane in TMOS in different ratios.…”

Synthesis of novel functional liquid and its application as a modifier in SBR/silica composites

“…Due to the high polarity of silica particles, the dispersion of silica in silane included systems and controllability of the performance are far from satisfactory. Ionic liquid (IL), a kind of fascinating molten salt with nearly zero vapor pressure and high thermal stability [5][6][7], has demonstrated high affinity toward various kinds of solid, such as carbon nanotubes [8][9][10][11][12][13][14], silica [15][16][17] and clays [18]. Various interactions, including cation-π interaction [8][9][10][11]19], van der Waal forces [13], delocalized electron interaction [14] and hydrogen bonding [16,18] have been well acknowledged and therefore subjected to a plenty of applications [14,[16][17][18][20][21][22][23][24][25][26].…”

Property variation of ionic liquid [Bmim][AuCl4] immobilized on carboxylated polystyrene submicrospheres with a small surface area

“…To determine the effect of immobilization on the T m of [5,9,[12][13][14] in which a significant T m depression is also observed when ILs are immobilized or confined to the solid surfaces. However, the degree of depression in this work is lower than previously reported values, most likely due to the much larger diameter of the submicrospheres and different surface groups used in this study.…”