TY - JOUR
T1 - Fatty acid langmuir films on liquid mercury
T2 - X-ray and surface tension studies
AU - Kraack, H.
AU - Ocko, B. M.
AU - Pershan, P. S.
AU - Sloutskin, E.
AU - Tamam, L.
AU - Deutsch, M.
PY - 2004/6/22
Y1 - 2004/6/22
N2 - The structure and phase behavior of liquid-mercury-supported molecular films of fatty acids (CH3(CH2)n-2COOH, denoted CnOOH) were studied for molecular lengths 7 ≤ n ≤ 24, by surface tensiometry and X-ray methods. Two qualitatively different film structures were found, depending on coverage. For high coverage, the film consists of a monolayer of roughly surface-normal molecules, showing a pressure-dependent sequence of structures similar, though not identical, to that of the corresponding water-supported Langmuir films. At low coverage, phases consisting of surface-parallel molecules are found, not observed on the aqueous subphases employed to date. In this range, a two-dimensional (2D) gas followed by a single and, for 14 ≤ n ≤ 24, also by a double layer of surface-parallel molecules is found as coverage is increased. Depending on chain length, the flat-lying phases have a crystalline 2D- ordered, a smectic-like 1D-ordered, or a disordered in-plane structure consisting of molecular dimers. The structure and thermodynamics of the films are discussed.
AB - The structure and phase behavior of liquid-mercury-supported molecular films of fatty acids (CH3(CH2)n-2COOH, denoted CnOOH) were studied for molecular lengths 7 ≤ n ≤ 24, by surface tensiometry and X-ray methods. Two qualitatively different film structures were found, depending on coverage. For high coverage, the film consists of a monolayer of roughly surface-normal molecules, showing a pressure-dependent sequence of structures similar, though not identical, to that of the corresponding water-supported Langmuir films. At low coverage, phases consisting of surface-parallel molecules are found, not observed on the aqueous subphases employed to date. In this range, a two-dimensional (2D) gas followed by a single and, for 14 ≤ n ≤ 24, also by a double layer of surface-parallel molecules is found as coverage is increased. Depending on chain length, the flat-lying phases have a crystalline 2D- ordered, a smectic-like 1D-ordered, or a disordered in-plane structure consisting of molecular dimers. The structure and thermodynamics of the films are discussed.
UR - http://www.scopus.com/inward/record.url?scp=3042680171&partnerID=8YFLogxK
U2 - 10.1021/la049977y
DO - 10.1021/la049977y
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C2 - 15986676
SN - 0743-7463
VL - 20
SP - 5375
EP - 5385
JO - Langmuir
JF - Langmuir
IS - 13
ER -