Vibrational spectra, orientations, and phase transitions in long-chain amphiphiles at the air/water interface: Probing the head and tail groups by sum frequency generation

Journal Article · Thu Dec 22 00:00:00 EST 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100102a045· OSTI ID:6617954

Zhang, D; Gutow, J; Eisenthal, K B ^[1]

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1. Columbia Univ., New York, NY (United States)

IR + visible sum frequency generation (SFG) has been used to obtain the vibrational spectra and orientations for both the nitrile (CN) head group and the methyl (CD[sub 3]) tail of the insoluble long-chain amphiphile CD[sub 3](CH[sub 2])[sub 19]CN at the air/water interface. The results show that the orientations of the head group and the terminal group vary with amphiphile surface density, but in markedly different ways. It is found at the amphiphile density, which corresponds to the phase transition from the gas/liquid coexistence region to the liquid region, that the hydrogen bonds of the CN head groups to water are broken, the water is squeezed out of the monolayer, and the orientation of the head group changes sharply. The possibility that the rupturing of the hydrogen bonds and reorientation of the CN head groups may be the trigger for the phase transition is discussed. In addition to the SFG study of the amphiphile at the air/water interface, a method was discovered that enables SFG to remove the ambiguity in the ratio of the two Raman polarizability elements for a symmetric stretch. 30 refs., 6 figs.

• OSTI ID: 6617954
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 98:51; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DEUTERIUM COMPOUNDS
ABSORPTION SPECTRA
GAS CHROMATOGRAPHY
NUCLEAR MAGNETIC RESONANCE
PHASE TRANSFORMATIONS
NITRILES
AIR
CHEMICAL BONDS
INFRARED RADIATION
INTERFACES
LASERS
WATER
CHROMATOGRAPHY
ELECTROMAGNETIC RADIATION
FLUIDS
GASES
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
RADIATIONS
RESONANCE
SEPARATION PROCESSES
SPECTRA
400201* - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures