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Investigation of monolayer interactions by wave attenuation and surface pressure studies
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|Title:||Investigation of monolayer interactions by wave attenuation and surface pressure studies|
|Abstract:||A method for accurate determination of the damping coefficient and wave number for the capillary ripple experiments was developed. Mixed monolayers of cholesterol and lecithin were subjected to the ripple experiments and finally interaction between cholesterol and hexadecyltrimethyl ammonium bromide (HDTAB) was studied by the help of surface pressure area measurements. In the capillary ripple experiment, an oscillating probe was used to generate ripples at the interface. A sensing probe lying parallel to the generating probe and fitted to a piezoelectric cartridge converted the wave motion to an electrical signal. The rms voltage output from the cartridge was proportional to the wave amplitude. The amplitude was observed at a particular frequency and the probe separation varied systematically to note the amplitude at each separation. The data set was then treated by the least squares method to fit the expression for the standing wave motion between the probes. The damping coefficient, wave number, probe shift and amplitude reflection at the boundaries and the amplitude of the sending probe were treated as adjustable parameters and the set of values obtained for which the least squares sum showed a minimum. The value of the damping coefficient and wave number were obtained to within an accuracy of 1%. Values of the parameters were obtained at different frequencies for the air-water interface. A variation of this method was applied to mixed monolayers of cholesterol and dipalmitoyl lecithin as well as to the monolayers of the pure substance themselves. In addition to the ripple damping coefficient and wave number, surface pressure was measured with a modified Langmuir-Adam film balance. The values of the viscoelastic parameters of the monolayers were plotted against the film pressure. The curves showed a molecular interaction between cholesterol and lecithin at low surface pressures. The monolayer interaction of cholesterol with HDTAB was studied by the help of surface pressure area investigations. The results show the formation of a 1:1 complex between the two substances. Kinetics of diffusion of HDTAB from the interface to the bulk were studied and the first order rate constant determined.|
Thesis (Ph. D.)--University of Hawaii, 1969.
Bibliography: leaves -87.
vii, 87 l illus
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|Appears in Collections:||Ph.D. - Chemistry|
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