Coexistences of lamellar phases in ternary surfactant solutions

Isamu Sou, Ryuichi Okamoto, Shigeyuki Komura, Jean Wolff

Research output: Contribution to journalArticlepeer-review


We theoretically investigate the coexistences of lamellar phases both in binary and in ternary surfactant solutions. The previous free energy of a lamellar stack is extended to take into account the translational entropy of membrane segments. The obtained phase diagram for binary surfactant solutions (surfactant/water mixtures) shows a phase separation between two lamellar phases and also exhibits a critical point. For lamellar phases in ternary surfactant solutions (surfactant/surfactant/water mixtures), we explore the possible phase behaviors and show that the phase diagrams exhibit various three-phase regions as well as two-phase regions in which different lamellar phases coexist. We also find that finite surface tension suppresses the undulation fluctuations of membranes and leads to a wider three-phase and two-phase coexistence regions.

Original languageEnglish
Pages (from-to)272-281
Number of pages10
JournalSoft Materials
Issue number4
Publication statusPublished - Oct 2 2017
Externally publishedYes


  • Helfrich interaction
  • Lamellar phase
  • phase behaviors
  • surfactant solutions

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics


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