Highly viscoelastic wormlike micellar solutions formed by cationic surfactants with long unsaturated tails

Srinivasa R. Raghavan, Eric W. Kaler

Research output: Contribution to journalArticlepeer-review

368 Scopus citations

Abstract

Cationic surfactants having long (C22) mono-unsaturated tails were studied in aqueous solutions containing salt using steady and dynamic rheology. The surfactant erucyl bis(hydroxyethyl)methylammonium chloride self-assembles into giant wormlike micelles, giving rise to unusually strong viscoelasticity. Under ambient conditions, the viscosity enhancement due to surfactant exceeds a factor of 107. Some samples behave as gel-like solids at low temperatures and revert to the viscoelastic (Maxwellian) response only at higher temperatures. These samples display appreciable viscosities (> 10 Pa·s) up to very high temperatures (ca. 90°C). Salts with counterions that penetrate into the hydrophobic interior of the micelles, such as sodium salicylate, are much more efficient at promoting self-assembly than salts with nonbinding counterions, such as sodium chloride. Changing the surfactant headgroup to the more conventional trimethylammonium group reduces the viscosity at high temperatures.

Original languageEnglish (US)
Pages (from-to)300-306
Number of pages7
JournalLangmuir
Volume17
Issue number2
DOIs
StatePublished - Jan 23 2001

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