PH-dependent appearance of chiral structure in a langmuir monolayer

A. Datta, J. Kmetko*, C. J. Yu, A. G. Richter, K. S. Chung, J. M. Bai, P. Dutta

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Grazing incidence X-ray diffraction studies on a heneicosanoic (C 21) acid monolayer with cadmium ions in the subphase, at near-zero surface pressure and ∼9 °C, show that there exists a pH "window" within which the monolayer takes on a chiral structure and an ordered superlattice is also observed. Below this pH window, the monolayer has a tilted structure like that of a pure fatty acid monolayer at low pressures, indicating negligible headgroup-ion interaction. Above the window, the monolayer goes to a structure very similar to the high-pressure untilted S phase seen in pure fatty acid monolayers. The chiral structure is never seen when cadmium is replaced by zinc, another divalent metal with only slightly lower electronegativity, or (as reported earlier) with calcium. Raising temperature within the cadmium pH window destroys the superlattice and takes the monolayer to the backbone-disordered Rotator-I structure.

Original languageEnglish (US)
Pages (from-to)5797-5802
Number of pages6
JournalJournal of Physical Chemistry B
Issue number24
StatePublished - Jun 22 2000

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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