Interfacial and Bulk Properties of the New Fluorocarbon−Hydrocarbon Hybrid Unsymmetrical Bolaform Surfactant

Abstract

We report the interfacial properties of a new fluorocarbon−hydrocarbon hybrid surfactant [OH(CH2)11N+(C2H4)2(CH2)2(CF2)5CF3 I-, or FHUB], which has a fluorocarbon chain as well as a ω-hydroxyalkyl chain. This new hybrid surfactant has properties that are different than classical hydrocarbon- and fluorocarbon-containing surfactants. This difference is created by combining a fluorocarbon chain and the hydrocarbon chain in a way to give the best performance (i.e., low critical micellization concentration, low limiting surface tension, salt insensitivity). The unsymmetrical bolaform character of FHUB gives rise to the salt-insensitive interfacial behavior of this surfactant. The presence of the fluorocarbon chain reduces the critical micelle concentrations of this new hybrid surfactant to a lower value (0.5 mM in 100 mM LiBr) compared to classical ionic and unsymmetrical bolaform surfactants such as dodecyltrimethylammonium bromide (2.5 mM in 100 mM LiBr) and (11-hydroxyundecyl)trimethylammonium bromide (21 mM in 100 mM LiBr). Moreover, the presence of the more rigid hydrophobic part (fluorocarbon chain) affects the aggregation properties of FHUB. The FHUB molecules start to form aggregates with less curvature at a low surfactant concentration. The formation of small aggregates, which have been reported to form by unsymmetrical bolaform surfactants, is prevented. As a result, the limiting surface tension of FHUB is obtained as a low value. The aggregate size of FHUB shows an increase first, goes through a maximum, and decreases with an increase at the surfactant concentration. The solubilization of water-insoluble dye within the aggregates is also determined to be a function of the surfactant concentration.