Spontaneous vesicle formation and phase behavior in mixtures of an anionic surfactant with imidazoline compounds

Yamaira I. González, Maria Stjerndahl, Dganit Danino, Eric W. Kaler*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Unexpected colloidal assemblies form in aqueous mixtures of sodium dodecylbenzenesulfonate (SDBS) with the following imidazoline compounds: 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (V-44, which is a commonly used free-radical initiator), 2,2′-tetramethylenedi-2- imidazoline (TMI), and the main recombination product (RP) from the decomposition of V-44. All of these imidazoline compounds act as hydrotropes. As the molar ratio of imidazoline to SDBS increases, a gradual transition from micelles to vesicles to bilayers to precipitate is observed. V-44 decomposes slowly at 25°C, and the phase diagrams of V-44/SDBS and RP/SDBS are similar. The vesicular region observed in mixtures of TMI/SDBS is larger in composition than that of V-44/SDBS and RP/SDBS mixtures. At equimolar compositions of SDBS and RP, a novel colloidal structure with multiple closely packed bilayers is observed. In these mixtures, small unilamellar vesicles (<80 nm in diameter) form spontaneously, although with time they coexist with a small amount of precipitate and their size increases steadily. The self-assembly of vesicles occurs over a wide range of compositions when the solution pH is lower than the pK a of the imidazoline moiety, Quasi-elastic light scattering, cryogenic transmission electron microscopy, nuclear magnetic resonance, and small-angle neutron scattering were used to determine the characteristic length scales and properties of the assemblies.

Original languageEnglish
Pages (from-to)7053-7063
Number of pages11
JournalLangmuir
Volume20
Issue number17
DOIs
StatePublished - 17 Aug 2004
Externally publishedYes

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