Self-Assembly of Long-Chain Betaine Surfactants: Effect of Tailgroup Structure on Wormlike Micelle Formation

Veena T. Kelleppan, Jackson E. Moore, Thomas M. McCoy, Anna V. Sokolova, Liliana De Campo, Brendan L. Wilkinson, Rico F. Tabor

Research output: Contribution to journalArticleResearchpeer-review

55 Citations (Scopus)


Long-chain amidopropyl betaines are known for their ability to self-assemble into viscoelastic wormlike micellar structures. Here, we explore the effect of tailgroup molecular architecture on this process, comparing five molecules, each with C18 chains but different levels of unsaturation and branching. The surfactants are synthesized from stearic, oleic, linoleic, linolenic, and isostearic acids. The self-assembly of these molecules in aqueous solutions is explored using small- and ultra-small-angle neutron scattering (SANS and USANS). It is seen that optimum wormlike micelle formation is achieved for the oleic-chained surfactant, and the alignment of self-assembled structures is further explored using rheo-SANS. The more highly unsaturated molecules form rodlike micelles, whereas the stearic-tailed molecule shows a pronounced Krafft point and the isostearic-chained surfactant is entirely water-insoluble. These results demonstrate the critical importance of tailgroup geometry on surfactant properties and self-assembly for this industrially important class of surfactants.

Original languageEnglish
Pages (from-to)970-977
Number of pages8
Issue number3
Publication statusPublished - 23 Jan 2018

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