Thiophene‐based ionic liquids: synthesis, physical properties, self‐assembly, and oxidative polymerization

Abstract Preparation and polymerization of methylimidazolium‐based ionic liquids (ILs) that incorporate a thiophene moiety at the terminus of a C10 alkyl chain are described. Both a bromide and nitrate salt of the amphiphilic thiophene IL self‐assembles in water (albeit the nitrate to a lesser extent), adopting columnar mesophases. Polarized optical microscopy and small‐angle X‐ray scattering (SAXS) studies show that at low water content the IL–water binary mixtures form liquid crystalline mesophases possessing significant short‐range ordering due to strong π interactions between adjacent thiophene moieties. At higher water content, the short‐range ordering is lost, but long‐range ordering persists up to ca. 45% (w/w) water. The chemical oxidative coupling of the nitrate monomer yields a highly water‐soluble polymer. Electrochemical studies show that the polymer possesses a high oxidation potential (1.95 V) and thus, is resistant to chemical doping. In dilute aqueous solution, electronic absorption spectroscopy and X‐ray scattering show the polymer adopts a random, coil‐like conformational state. Slight improvement in the polymer conformation can be achieved by exchange of the counter anion. Copyright © 2008 John Wiley & Sons, Ltd.