Ionic Liquids Containing Silsesquioxane and Cyclic Siloxane Frameworks

Abstract

AbstractThis paper describes the author's recent work on the preparation and properties of thermally stable ionic liquids (ILs) containing siloxane frameworks. Quaternary ammonium and imidazolium salt‐type ILs containing random oligosilsesquioxane frameworks were successfully prepared via the hydrolytic condensation of the corresponding organotrialkoxysilanes by using an aqueous superacid bis(trifluoromethanesulfonyl)imide (HNTf2) solution as a catalyst and solvent. Imidazolium salt‐type ILs containing polyhedral oligomeric silsesquioxane (POSS) frameworks were also prepared through a reaction similar to that described above by using a water/methanol mixed solution of HNTf2. In addition, amorphous POSSs with two types of ionic groups randomly distributed in the side chain were prepared. These POSSs were ILs exhibiting fluidity at relatively low temperatures. Furthermore, imidazolium and ammonium salt‐type ILs containing cyclic oligosiloxane frameworks were prepared through a reaction similar to that of the corresponding organodialkoxysilanes. The thermal decomposition temperatures of the above ILs containing siloxane frameworks were higher than those of general ILs.