Confinement-induced symmetry breaking of interfacial surfactant layers

F.A.M. Leermakers, L.K. Koopal, T.P. Goloub, A.W.P. Vermeer, J. Kijlstra

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)

Abstract

Interaction forces between mesoscopic objects are fundamental to soft-condensed matter and are among the prime targets of investigation in colloidal systems. Surfactant molecules are often used to tailor these interactions. The forces are experimentally accessible and for a first theoretical analysis one can make use of a parallel-plate geometry. We present molecularly realistic self-consistent field calculations for an aqueous nonionic surfactant solution near the critical micellization concentration, in contact with two hydrophobic surfaces. The surfactants adsorb cooperatively, and form a monolayer onto each surface. At weak overlap the force increases with increasing compression of the monolayers until suddenly a symmetry braking takes place. One of the monolayers is removed jump-like and as the remaining monolayer can relax, some attraction is observed, which gives way to repulsion at further confinement. The restoring of symmetry at strong confinement occurs as a second-order transition and the force jumps once again from repulsion to attraction. It is anticipated that the metastable branch of the interaction curve will be probed in a typical force experiment. Under normal conditions pronounced hysteresis in the surface force is predicted, without the need to change the adsorbed amount jump-like
Original languageEnglish
Pages (from-to)8756-8763
JournalThe Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
Volume110
Issue number17
DOIs
Publication statusPublished - 2006

Keywords

  • field lattice model
  • nonionic surfactants
  • ionic surfactants
  • statistical thermodynamics
  • adsorption regulation
  • adsorbed layer
  • phase-behavior
  • aqueous film
  • association
  • hydrophobicity

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