Thermodynamics of phase transitions in Langmuir monolayers observed by vibrational sum frequency spectroscopy

Marc C. Gurau, Edward T. Castellana, Fernando Albertorio, Sho Kataoka, Soon Mi Lim, Richard D. Yang, Paul S. Cremer

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Vibrational sum-frequency spectroscopy (VSFS) was used to study gauche defects in octadecylamine (ODA) monolayers at the air/water interface. The VSFS spectra provide unique insights into phase transitions that occur as a result of changes in the structure of the monolayer's hydrophobic region. These changes can be attributed to the increased presence of gauche conformers in the ODA alkyl chains during the monolayer's transition from the solid to liquid phase. Temperature-dependent spectra from monolayers at several different pressures were used to assign the phase transition temperature based on the observed changes in microscopic structure. Through application of a two-dimensional form of the Clapeyron equation, the first in situ measurements of the entropy and enthalpy changes associated with gauche conformers in a monolayer were made.

Original languageEnglish (US)
Pages (from-to)11166-11167
Number of pages2
JournalJournal of the American Chemical Society
Volume125
Issue number37
DOIs
StatePublished - Sep 17 2003

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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