X-ray diffraction study of heneicosanol monolayers on the surface of water

Journal Article · Tue Sep 15 04:00:00 EDT 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.463891· OSTI ID:7018138

Shih, M C; Bohanon, T M; Mikrut, J M ^[1]; Zschack, P ^[2]; Dutta, P ^[1]

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1. Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208 (United States)
2. Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States)

We have studied Langmuir monolayers of CH{sub 3}(CH{sub 2}){sub 20}OH (heneicosanol) using x-ray diffraction. Over the temperature range 7--55 {degree}C, the monolayer isotherms show only one discontinuity, which may be either a flat section'' or a kink;'' we find that these are transitions between tilted and untilted phases. There are several untilted phases, with hexagonal and distorted-hexagonal structures, as in monolayers of the corresponding (heneicosanoic) acid. However, in contrast to the acid, when the pressure is lowered the molecules tilt only towards a next-nearest neighbor. The dependence of the lattice spacings on pressure and temperature indicate that the monolayer does not form a tilted hexagonal'' phase, even at temperatures where the untilted phase is hexagonal (rotator-II).

• DOE Contract Number: FG02-84ER45125
• OSTI ID: 7018138
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 97:6; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ADSORPTION
ALKYL RADICALS
COHERENT SCATTERING
DIFFRACTION
FILMS
HYDROGEN COMPOUNDS
HYDROXIDES
ISOTHERMS
LAYERS
METHYL RADICALS
MOLECULES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PRESSURE DEPENDENCE
RADICALS
SCATTERING
SORPTION
SURFACE PROPERTIES
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
WATER
X-RAY DIFFRACTION