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 journalArticle

36 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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