Surface Tension Anisotropy and Relaxation in Uniaxially Compressed Langmuir Monolayers

T. M. Bohanon*, A. M. Lee, J. B. Ketterson, P. Dutta

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

We have performed capillary wave measurements, both parallel and perpendicular to the direction of compression, on uniaxially compressed Langmuir films. We observed surface tension anisotropy only in the A and B (CS and L2″) phases of heneicosanoic acid. These are also the phases whose reported X-ray diffraction peak widths are resolution limited. When surface tension anisotropy developed, it decayed only slightly over 30 min. Surface pressure measurements are ambiguous for phases in which the surface tension is anisotropic. At room temperature, where uniaxially compressed acid monolayers are isotropic, calcium ions caused anisotropy only at the highest pH values (≈11), even though the films are known to be stiff at moderate pH values (≈6). We observed a large change in surface tension anisotropy with a small change in pH, signaling a phase transition.

Original languageEnglish (US)
Pages (from-to)2497-2500
Number of pages4
JournalLangmuir
Volume8
Issue number10
DOIs
StatePublished - Oct 1 1992

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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