Monolayer spreading

Fig. IV-14. Resonance Raman Spectra for cetyl orange using 457.9-nm excitation. [From T. Takenaka and H. Fukuzaki, Resonance Raman Spectra of Insoluble Monolayers Spread on a Water Surface, J. Raman Spectr., 8, 151 (1979) (Ref. 157). Copyright Heyden and Son, Ltd., 1979 reprinted by permission of John Wiley and Sons, Ltd.]...

Bailey, A.L, Cardenas-Valera, A.E., Doroszkowsi, A., Graft copolymers as stabilizers for oil-in-water emulsions. Part 1. Synthesis of the copolymers and their behaviour as monolayers spread at the air-water and oil-water interfaces. Colloids and Surfaces, v.96, pp.53-67, 1995. 

A C60 derivative with an attached fluorinated chain gave a limiting area of 0.78 nm molecule [266]. It was reported that this film was so mechanically rigid that it pushed the Wilhehny plate out of the water at 11 14 mN m The monolayer spreading of this compound arises from the even greater hydrophobicity of the fluorocarbon chains and their orientation away from the water surface. The LB films with a fluorinated tetrathiafulvalene derivative did not show evidence of charge transfer in their UV spectra. 

The Yl/A isotherms of the racemic and enantiomeric forms of DPPC are identical within experimental error under every condition of temperature, humidity, and rate of compression that we have tested. For example, the temperature dependence of the compression/expansion curves for DPPC monolayers spread on pure water are identical for both the racemic mixture and the d- and L-isomers (Fig. 13). Furthermore, the equilibrium spreading pressures of this surfactant are independent of stereochemistry in the same broad temperature range, indicating that both enantiomeric and racemic films of DPPC are at the same energetic state when in equilibrium with their bulk crystals. 

Fig. 13 Force/area curves of dipalmitoylphosphatidyl choline monolayers spread on pure water at 25°C (solid line) and 45°C (dashed line). The compression rate is 7.2 A2/molecule per minute. The shape of the isotherms is identical for homochiral and heterochiral films.

N-Stearoyltyrosine. The case of N-stearoylserine methyl ester illustrates temperature-dependent enantiomeric discrimination in both monolayers spread from solution and in equilibrium with the bulk phase. Although the IIIA isotherms suggested large differences in the intermolecular associations in homochiral and heterochiral films of SSME, there exist chiral systems in which enantiomeric discrimination as exhibited in film compression properties is much more subtle. N-Stearoyltyrosine (STy) is such a system. 

Figures 51(A-C) give the compression and expansion cycles for the two isomers of the C-15 6,6 -A diacids at 25, 30 and 35°C. At 30°C, the energetics of compression of the second eluting C-15 6,6 -A diacid are similar to those of the second eluting C-12 6,6 -A diacid at 25°C. Raising the temperature causes a weakening of the intermolecular interactions in the monolayer spread...

It has been shown by Harvey et al. (1989) that incorporation of palmitic acid into a monolayer spread from stearoylserine methyl ester (SSME) breaks up intermolecular SSME interactions. The palmitic acid acts as a two-dimensional diluent. Figures 52(A-C) give the Yl/A isotherms for mixtures of FE and SE C-15 6,6 -A with palmitic acid. Dilution of the monolayer cast from the second eluting isomer with 15 mol% palmitic acid separates the diacid molecules from one another on the water surface and perhaps allows for the expression of their stereochemically dependent conformations. The mixed film (15% palmitic acid/85% C-15 6,6 -A) expands at low II and behaves in much the same manner as the single-component monolayer (C-15 6,6 -A) behaves at 30°C. Addition of 15 mole% palmitic acid into a monolayer cast from the FE C-15 diacid has little effect on its energetics of compression, indicating a stronger intermolecular interaction afforded by its stereochemically dependent conformation at the air-water interface. 

The two compartment trough is schematically shown in Fig. 12. The trough is divided to two large compartment, where monolayer is spread, and a small buffer portion by two fixed barriers with a flexible gate. Compression of monolayers spread on each compartment is controlled independently by two movable polytetrafluoroethylene (PTFE) barriers. A substrate can move from a compartment to the other compartment by passing through the flexible gates... 

Mechanism forming a thin film in an epitaxial relation through a monolayer spreading parallel to the interface. This is called the Frank-van der Merve mechanism. 

Frank-van der Merve (strong adsorption, saturated to bulk phase) Monolayer spreading parallel to the interface — niAal/othin film) A/u >0 (thick film) Aa < 0 or 2a < a Cj — e [Pg.144]

Gold particulate films have been formed under thiol monolayers spread on aqueous HAuC14 solutions by exposure to carbon monoxide exposure [110]. 

Fig. 94. Absorption spectra of gold particulate films formed under thiol monolayers spread on aqueous HAuC14 solutions exposed to CO prior (a) and subsequent (b) to annealing at 140 °C for 10 min (unpublished results)...

INSOLUBLE MONOLAYERS SPREADING OF SURFACTANTS ON AQUEOUS SURFACES... 

Figure 1. Effect of pH on surface pressure of a BSA monolayer spread on distilled water subsequently injected with SDS...

Figure 2. Surface pressure, potential, and viscosity vs. molecular area of stearic acid monolayers spread at air-water interface over substrates containing ammonium and alkali metal cations (0.5N). 30° C., rapid compression...

Figure 3. Surface viscosity vs. molecular area for palmitic, stearic, and behenic acid monolayers spread on 0.5N NaOH substrates at 30°C.

Figure 4. Surface pressure vs. molecular area for palmitic acid monolayers spread on aqueous substrates of varying pH at 30°C. and 0.5N total cation concentration (KOH + KCl). Rapid compression...

Fig. 6.3. Surface pressure-area ( II-A ) curves for a microbubble-surfactant monolayer spread at the air/(distilled) water interface. (Note that area is expressed as m2/mg protein in this figure and Figs. 6.4 and 6.5, which is also equivalent to m2/110 mg of microbubble-surfactant mixture. See text for further discussion. Taken from ref. 361.)...

Fig. 6.4. Surface pressure-area ( II-A ) curves for microbubble-surfactant monolayers spread on various aqueous subphases. (Taken from ref. 361.)...

Studies on polymer monolayers spread at air - water interface to characterize their physical properties, as surface pressure, -it, surface potential, AV, surface viscosity, t S, and surface rigidity [39,40] have been reported abundantly. 

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