Alcohols monolayers

Fig. IV-13. Example of a p-polarized reflection spectrum from Ref. [154] for a stearyl alcohol monolayer on water. The dashed line is the baseline to be subtracted from the spectra. [Reprinted with permission from Joseph T. Buontempo and Stuart A. Rice, J. Chem. Phys. 98(7), 5835-5846 (April 1, 1993). Copyright 1993, American Institute of Physics.]...

The experimental points on curve 1 indicate that some of the thick films transform into NBF, since the potential of the double diffuse electric layer at the decyl alcohol monolayer/air interface is low (energy barrier ITmax in the IT(/i) isotherm. This transition was observed only at temperature below 10°C. Under such conditions a condensed monolayer from n-alcohol forms at the solution/air interface [396]. Metastable films were also observed in the temperature range of 8-10°C, i.e. thick films were produced which transformed into NBF very easily (within a short time) [394]. Therefore, there is a complete similarity with NBF formation from soluble monolayers of various surfactants, i.e. the presence of a close packing in this monolayer is a necessary condition for formation of NBF. 

Shah, D. O. and Shiao, S. Y. (1975). The chain-length compatibility and molecular area in mixed alcohol monolayers. In Goddard, E. D., ed. Monolayers, Advances in Chemistry Series 144 Am. Chem. Soc., Washington, DC, pp. 153-164. 

Past efforts to target a specific deposition site were based on the control of particle size at inhalation. Also, efforts to control growth of particles by adding substances with surfactant properties have been reported. Addition of lauric and capric acids to disodium fluorescein markedly reduces particle growth [22], as does the addition of a cetyl alcohol monolayer to saline droplets [23], Such a reduction of growth would be expected to facilitate particle penetration to more... 

The previous part showed that inverse gas chromatography is a very useful tool in the investigation of long-chain aliphatic alcohol monolayers adsorbed on the surface of porous silica gel. Now a simple theoretical model of the adsorbed layer that can be used to analyse the experimental data obtained by inverse gas chromatography is considered. The model is based on the theory of adsorption of simple gases on solid surfaces and, initially restricted to fully localized adsorption [36-38], was extended to treat also long chain molecules [39]. 

The Chain-Length Compatibility and Molecular Area in Mixed Alcohol Monolayers... 

Figure 1. Surface pressure-area curve of stearyl alcohol monolayer at pH 2.0, 25°C. Compression rate 6.5 A2/molecule/min.

Figure 1 shows the surface pressure—area curve of stearyl alcohol monolayer at pH 2.0 and 25 °C, where Ae is the area/molecule in the expanded state at zero surface pressure, Ac is the area/molecule in the condensed state at zero surface pressure, and A2o is the area/molecule at surface pressure of 20dynes/cm. Figure 2 shows the values of Ae, Ac, and A2o for various alkyl alcohols. From this diagram the average area per molecule in mixed monolayers was calculated using simple additivity rule. Figure 3 shows the excess molecular area when Ci6 alkyl alcohol... 

The results on the surface pressure-area curve of stearyl alcohol monolayer shown in Figure 1 and the area/molecule of other alkyl alco-... 

The original work carried out by Langmuir was the ability to form and transfer monolayers of fatty acid, ester and alcohol monolayers onto solid substrates. Several years later, Katherine Blodgett showed that multilayer films can also be formed and transferred onto solid substrates. The ability to transfer layers of organic material from a liquid phase, typically water, to a solid substrate allows the careful construction of ordered layer structures at a molecular level... 

Majewski J, Popovitzbiro R, Kjaer K, Alsnielsen J, Lahav M, Leiserowitz L (1994) Toward a determination of the critical size of ice nuclei - a demonstration by grazing-incidence X-ray-diffraction of epitaxial-growth of ice under the C31H630H alcohol monolayer. J Phys Chem 98 4087 093... 

To examine the effect of permeant size and amphiphile chain length on molecular transfer, studies have been carried out on the diffusion of Br2 across a water-air interface modified with different chain length fatty alcohols [40]. The principles of these experimental measurements, which employed the SECM-double potential step chronoamperometric (DPSC) mode, are illustrated in Figure 13.13. An initial (forward) potential step was employed to electrogenerate Br2 by the diffusion-controlled oxidation of Bf in an aqueons snlfuric acid subphase. Tip-generated Br2 diffused to and transferred across the fatty alcohol monolayer (Fignre 13.13a). Br2 was then collected back by... 

FIGURE 13.11 Schematic illustration (not to scale) of the SECM-induced transfer of oxygen across a long-chain alcohol monolayer at the air-water interface. 

Zhang, J., Unwin, P R. Effect of fatty alcohol monolayers on the rate of bromine transfer across the air/ water interface Assessment of candidate models using scanning electrochemical microscopy. Langmuir 2002, 18, 1218. 

C20 alcohol monolayer allows only one third of the water loss related to evaporation of the pure cholesterol monolayer. This is presumably due to the fact that the C20 alcohol forms monolayers that are in the two-dimensional solid state. In contrast, the cholesterol monolayers are in the two-dimensional liquid state. However, when cholesterol is incorporated into a C20 alcohol monolayer, the cholesterol mole fraction needs to be only about 20% to liquefy the solid monolayers of C20 alcohol. The abrupt increase in evaporation rate of water at 20-25 mol% cholesterol illustrates the two-... 

It has been shown that mixed monolayers of oleic acid and cholesterol exhibit the minimum rate of evaporation at a 1 3 molar ratio of oleic acid to cholesterol. This is shown in mixed monolayers of oleic acid and cholesterol in Fig. 7 as a function of surface pressure [11]. In has further been shown that a 1 3 molar ratio in mixed fatty acid and fatty alcohol monolayers, one observes the maximum foam stability, minimum rate of evaporation, and maximum surface viscosity in these systems [12]. 

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