The Effect of Cation Structure on the Mesophase Architecture of Self‐Assembled and Polymerized Imidazolium‐Based Ionic Liquids

Abstract

AbstractThe binary phase behavior of a series of imidazolium‐based ionic liquids (ILs) has been investigated. In particular, the effect of two structural modifications of the imidazolium cation, alkyl chain length, and the introduction of a polymerizable acryloyl group at the alkyl chain terminus, has been studied using small angle X‐ray scattering. Upon increasing water content, the non‐polymerizable IL, 1‐decyl‐3‐methylimidazolium chloride, adopts mesophase structures of predominately two‐dimensional (2D) hexagonal symmetry, including structures intermediate in character between lamellae and 2D hexagonal micelles. Introduction of a photopolymerizable acryloyl functional group to form 1‐(10‐(acryloyloxy)decyl)‐3‐methylimidazolium chloride produces a rod‐coil IL cation that yields self‐assembled mesophases in which the formation of tetragonal morphologies is favored. Covalent linking of the IL cations by UV‐induced polymerization converts the lyotropic mesophase into three‐dimensional biocontinuous chemical gels. Reducing the alkyl chain length, as in the polymerizable IL cation 1‐(8‐(acryloyloxy)octyl)‐3‐methylimidazolium chloride, severely reduces the self‐assembled mesophase order, and triggers the formation of only weakly ordered one‐dimensional lamellar structures.magnified image