Ionic liquid (IL) 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO 4 ] has been immobilized in silica matrix by using nonhydrolytic one-pot sol−gel method, with tetraethyl orthosilicate (TEOS) used as precursor and formic acid as a reagent. The glass transition temperature (T g ) of the confined IL was ∼20 °C higher than the bulk IL. The thermal stability of IL also increased upon confinement. These changes are explained on the basis of interactions between the inorganic SiO 2 pore wall surface and the organic cation [EMIM] + and anion [EtSO 4 ] − of the ionic liquid. Quantum mechanical calculation based on DFT has been used to show that the oxygen of SiO 2 interacts with the C−H of the imidazolium ring of [EMIM] + cation and the surface Si atoms interact with S−O of the [EtSO 4 ] − anion. The latter has led to Si−O−S linkages, which have been experimentally confirmed by FTIR studies. The silanol OH group is also likely to interact but less dominantly as compared to the earlier discussed interaction. These interactions have also led to changes in the fluorescence spectra of the confined IL.

In the present study, immobilization of different amounts of ionic liquid (IL) 1-ethyl-3-methyl imidazolium tetrafluoroborate [EMIM][BF4] into the pores of ordered mesoporous MCM-41 (Mobil Composition of Matter no. 41) has been accomplished successfully.

H nuclear magnetic resonance relaxometry is applied to investigate the translational and rotational dynamics of ionogels composed of an ionic liquid (IL): 1-ethyl-3-methyl-imidazolium-thiocyanate (EMIM-SCN) confined in a nanoporous SiO matrix. The relaxation studies were performed in the frequency range of 4 kHz-40 MHz and the temperature range of 223-248 K for different concentrations of the IL; the ratio (no. of moles of IL/no. of moles of SiO) yields: 1/2, 3/5 and 7/10. A thorough analysis of this large set of experimental data was performed assuming the existence of two fractions of the liquid: a core fraction (near the pore center) and a surface fraction (near the confining walls). It was shown for all concentrations that the confinement does not significantly affect the translational motion near the pore center compared to the dynamics in bulk. The diffusion coefficients in the surface fraction are considerably smaller compared to the core fraction (from one to two orders of magnitude) and the difference becomes larger with increasing temperature. The diffusion coefficients become smaller for higher concentrations - this effect is not large, but visible. Very importantly, it was shown that, despite the interactions with the surface, the diffusion in the surface fraction remains of 3D character. As far as rotational dynamics in the surface fraction is concerned, it slows down compared to the bulk (and the core fraction), but this effect is of the order of factor 2-3.