Nonlinear shear response and anomalous pressure dependence of viscosity in a langmuir monolayer

R. S. Ghaskadvi, J. B. Ketterson, P. Dutta*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Scopus citations

Abstract

We have studied the strain response of heneicosanoic acid monolayers to an applied sinusoidal shear stress. We have measured the complex shear modulus (G = G′ + iG″) as a function of strain amplitude and frequency, monolayer pressure, and temperature. We find that G′ and G″ are independent of the strain only at very small strain amplitudes; beyond an 'elastic limit', both G′ and G″ decrease with increasing strain amplitude. G′ and G″ are discontinuous at the L2-L2′ and L2′-S phase transitions. In the low-pressure L2 phase, G′ and G″ first increase with increasing pressure and then anomalously decrease. Compared to existing X-ray data, we find an unexpected correlation: over a range of temperatures, the pressure at which G″ is a maximum is also the one at which the monolayer lattice is hexagonal (undistorted).

Original languageEnglish (US)
Pages (from-to)5137-5140
Number of pages4
JournalLangmuir
Volume13
Issue number19
DOIs
StatePublished - Sep 17 1997

ASJC Scopus subject areas

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

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