Formation of a Biomimetic, Liquid-Crystalline Hydrogel by Self-Assembly and Polymerization of an Ionic Liquid

Abstract

Preparation and polymerization of a methylimidazolium-based ionic liquid (IL) that incorporates an acryloyl moiety at the terminus of a C₈ alkyl chain is described. The IL monomer weakly self-assembles upon addition of water and oligomerizes on mild heating. Initiator-free polymerization (as evidenced by FT-IR spectroscopy) can be achieved by UV irradiation, forming an elastic, self-supporting hydrogel. Small-angle X-ray scattering (SAXS) studies on the unsupported polymer demonstrate that the hydrogel adopts an ordered lamellar structure. The polymer can absorb large quantities of water, swelling to nearly 200 times its original volume and, in the process, becoming a highly disordered lamellar structure. Swelling studies conducted using a range of organic solvents demonstrate that the polymer can also be swollen (albeit to a lesser extent) by polar, hydrogen-bonding solvents such as ethanol.