Effect of pressure on the thermotropic phase behavior of surfactant assemblies in water

Shoji Kaneshina, Michio Yamanaka

研究成果: Contribution to journalArticle査読

10 被引用数 (Scopus)

抄録

The temperature (T)-pressure (P) phase diagrams of aqueous solutions of a homologous series of cationic surfactants, tetradecyl- (C14TAB), hexadecyl- (C16TAB), and octadecyltrimethylammonium bromide (C18TAB), have been determined by observing the sudden change of the transmittance accompanying the phase transition under high pressure up to 160 MPa. Regarding three kinds of phase transitions which have been previously assigned by the differential scanning calorimetry (DSC) (S. Kaneshina and M. Yamanaka, J. Colloid Interface Sci.131, 493, 1989), all the transition temperatures were linearly elevated by applying pressure. The volume changes associated with the transitions were estimated from the Clapeyron-Clausius equation by using the values of the T-P slopes on the phase diagrams and of the transition entropies taken from the DSC study. A chemical potential vs pressure profile, of which slope reflects the partial molar volume, among the states of surfactant assemblies, i.e., micelle, gel, and coagel, was drawn schematically on the basis of the transition volumes. The phase boundary between the coagel phase and the micellar solution should be the critical solution line of the surfactant, representing the pressure dependence on the Krafft temperature. In the C18TAB-water system, the phase boundary line between the metastable gel and the supercooled micelle had a break point at 45 MPa, suggesting the existence of a new pressure-induced mesophase above 45 MPa. The metastable gel phase of C14TAB disappeared in the pressure range up to 160 MPa.

本文言語英語
ページ(範囲)474-480
ページ数7
ジャーナルJournal of Colloid And Interface Science
140
2
DOI
出版ステータス出版済み - 12 1990

All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • 生体材料
  • 表面、皮膜および薄膜
  • コロイド化学および表面化学

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