Oligoether carboxylate counterions: An innovative way towards surfactant ionic liquids

Recently, a new class of Ionic Liquids based on oligoether carboxylates was introduced, by our research group. This COncept of Melting Point Lowering due to EThoxylation (COMPLET) is now extended to cationic ammonium-based surfactants as counterions. The common requirement of a bulky headgroup for ionic liquid character is superseded by the presence of high flexibility in the molecular structure of the anion. These new salts of the 2,5,8,11-Tetraoxatridecan-13-oate acid (TOTOA) form room temperature Ionic Liquids up to a chain length of twelve carbon atoms of the ammonium ion. Viscosities even lower than those of the quaternary ammonium salts and conductivities in the range of the alkali salts are found. Results are discussed in terms of ion-pairing concepts as well as considering the possible complexation ability of the TOTO ion. This idea facilitates the conception of surfactant-like Ionic Liquids with a significantly improved eco-index, in terms of cytotoxicity and biodegradability, compared to classical/common systems. (C) 2017 Elsevier B.V. All rights reserved.