Backbone orientational order in fatty acid monolayers at the air-water interface

M. K. Durbin, A. G. Richter, C. J. Yu, J. Kmetko, J. M. Bai, P. Dutta

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


We report on the first observation of superlattice x-ray diffraction peaks (indicating herringbone ordering of the molecular cross sections) in a saturated fatty acid Langmuir monolayer. In the CS phase the “forbidden” (21) peak is observed with a resolution-limited width, implying that the herringbone order is long range. We also searched for this characteristic peak in the S, [Formula Presented] [Formula Presented] and [Formula Presented] phases. Although each phase displayed some higher-order peaks, only the lowest-temperature [Formula Presented] phase showed the herringbone peak. These results do not preclude the existence of short-range herringbone order in the other phases; a Landau theory of lipid monolayers [V. M. Kaganer and E. B. Loginov, Phys. Rev. Lett. 71, 2599 (1993)] predicts the existence of local herringbone order in some tilted phases, manifesting itself in the distortion of the molecular lattice from hexagonal. We have studied this distortion as a function of temperature along low-pressure isobars. The distortion goes to zero as the temperature is increased, but we do not see a first-order transition.

Original languageEnglish (US)
Pages (from-to)7686-7690
Number of pages5
JournalPhysical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
Issue number6
StatePublished - 1998

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Condensed Matter Physics


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