Mechanism of Concentration-Dependent Vesicle-Micelle Transition in Aqueous Mixture of Cationic and Anionic Surfactants

Hisanori Nakanishi, Koji Tsuchiya, Takahiro Ohkubo, Hideki Sakai, Masahiko Abe

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The phase behavior of aqueous mixed solution of cationic cetyltrimethyl-ammonium bromide (CTAB) and anionic sodium octylsulfate was studied focusing on the concentration-dependent vesicle-micelle transition. Dynamic light scattering measurements and freeze fracture TEM observations showed that the phase transition occurs in two steps depending on the total surfactant concentration. Equilibrium vesicles (V) formed in dilute solution was shown to transform to micelles (M) through a micelle/ small unilamellar vesicle (M + V) coexisting state. The concentration at which the transition from V to M + V occurs on the SOS-rich side lies around the CMC of pure SOS (120 mM). Moreover, electroconductivity and FT-IR measurements revealed that the phase transition is accompanied by a decrease in the degree of counter ion dissociation from surfactant molecules. Based on these experimental findings, the cause of the phase transition was discussed.

Original languageEnglish
Pages (from-to)443-451
Number of pages9
JournalJournal of Oleo Science
Volume54
Issue number8
DOIs
Publication statusPublished - 2005
Externally publishedYes

Keywords

  • electroconductivity
  • FF-TEM
  • FT- IR
  • micelle
  • mixed surfactant system
  • phase behavior
  • spontaneous vesicle

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

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