Formulation influence on the sol–gel formation of silica-supported ionogels

Abstract

Ionic liquids (ILs) present many new opportunities for the field of sol–gel chemistry. When conducted in an IL medium, sol–gel chemistry can produce novel silica structures as well as hybrid materials known as ionogels, which feature ILs supported by a solid scaffold material. In this work, the influence of reactive formulation on the properties of silica-supported ionogels is reported. A simple, non-hydrolytic sol–gel reaction between tetramethoxysilane and formic acid is employed to create silica-supported ionogels that exhibit wide variations in silica content, gelation time, and mechanical character. The influence of formulation on gelation time is demonstrated, and it is shown that a range of formulations can be used to produce soft, mechanically compliant ionogels. Furthermore, either brittle or compliant ionogels can be realized via rapid- or slow-gelling formulations. It is observed that the speed of gelation influences the pore structure in the resultant silica scaffold, thereby enabling different mechanical characters to be achieved for ionogels containing equivalent silica mass fractions.