A “worm”-containing viscoelastic fluid based on single amine oxide surfactant with an unsaturated C22-tail

Abstract

“Worm”-containing viscoelastic fluids formed by single C₂₂-tailed surfactants have attracted special interests over the past decade due to their unique rheological response. Here, a viscoelastic wormlike micellar solution of erucyldimethyl amidopropyl amine oxide (EMAO) was first reported and investigated. Upon increasing concentration, EMAO can self-assembly into micelles at a very low concentration, and then these micelles grow into long threadlike worms, which further entangle with each other in the semi-dilute region (>0.55 mM), enhancing the viscosity by several orders of magnitude. EMAO worms exhibit a smaller sensitivity to pH at room temperature than those of short-chain counterparts, but show evident pH responsiveness at high temperature due to the presence of multiple hydrogen bonds and cloud point, which is barely observed for short-chain amine oxide surfactants. The hydrogen bonds and cloud point also result in an uncommon thermo-thickening behaviour in a certain temperature range. Compared with short-chain amine oxide worms, EMAO worm possesses stronger thickening ability, better biodegradable and lower toxicity, giving it a rich prospective for use in gel cleaners, clear fracturing fluids, etc.