Catanionic Surfactant Self-Assembly in Protic Ionic Liquids

Saffron J. Bryant, Rob Atkin, Michael Gradzielski, Gregory G. Warr

Research output: Contribution to journalArticle

Abstract

Mixing of cationic and anionic surfactants in water can result in pseudo-double-tailed catanionic surfactant ion pairs that form lamellar phases or vesicles that are unstable toward electrolyte addition. Here we show that despite the very high ionic strengths, catanionic surfactants counterintuitively form a wider variety of self-assembled aggregates in pure ionic liquids (ILs, pure salts in a liquid phase) than in water, including micelles, vesicles, and lyotropic phases. Self-assembled structures only form when the IL is sufficiently polar to drive self-assembly through electrostatic interactions and/or H-bond networks, but the catanionic effect is manifested only when the IL does not itself exhibit pronounced amphiphilic nanostructure. This enables the type of catanionic aggregate formed to be designed by changing the hydrogen bonds between the ions through variation of the structures of the cation and anion. These results reveal an entirely new way of controlling catanionic surfactant self-assembly under nonaqueous and high-salt conditions.

Original languageEnglish
Pages (from-to)5926-5931
Number of pages6
JournalThe journal of physical chemistry letters
Volume11
Issue number15
DOIs
Publication statusPublished - 6 Aug 2020

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