Effect of synthesis conditions on the properties of an ionic liquid in the 1-butyl-3-methylimidazolium acetate - Na-bentonite ionogel. Steric stabilization and confinement

Abstract

For the first time, a comprehensive analysis has been done of the effect of synthesis conditions on the properties of an ionic liquid bound in the 1-butyl-3-methylimidazolium acetate - Na-bentonite ionogel. The ionogels were obtained by mechanical abrasion and through adsorption of 1-butyl-3-methylimidazolium acetate on Na-bentonite from acetone and a water-acetone solution. The prepared materials were characterized by X-ray diffraction, thermogravimetric and differential thermal analysis, FT-IR spectroscopy and dielectric spectroscopy. The obtained data made it possible to characterize the properties of the ionogel including the ionic liquid in different states – sterically stabilized by bentonite particles and being in the state of confinement in the nanopores of layered aluminosilicates. It has been found that introduction of an ionic liquid into the interlayer space of clay changes the dimensions of the basal spacing between the aluminosilicate plates. This is due to the packing density of the ionic liquid molecules between the clay layers. Confinement in clays also affects a number of other properties of ionic liquids. It has been shown that confinement causes changes in the IR-spectra of the ionic liquid, increases its thermal stability by 100 °C, and shifts the dielectric loss tangent on the dielectric relaxation spectrum towards lower frequencies.