Mixed Langmuir monolayer

Fig. 2.11 Mixed Langmuir monolayer of dialkylsiloxane and vitamin B12 erivative, and its transfer onto a solid substrate.

Figure 5 shows the 7t-A isotherm of the mixed Langmuir monolayer composed of a] -trans-P-carotene with harium stearate (1 10) at the air/water interface. The n-A isotherm shows a steep rise at the surface pressure above 15 mN/m. This observation confirms that the molecules in the monolayer are closely packed at the surface pressure of 30 mN/m, the value which corresponds to the fabricating condition when transferring the monolayer to the glass substrate. The limiting area, which corresponds to the area occupied by one molecule at the air/water interface, can be extrapolated from the steep part of the n-A isothermtobe 32 /molecule (see broken... 

Fig. 5.71-k isotherm at 18 C of the mixed Langmuir monolayer composed of all-trans- carotene and barium stearate (1 10) at the air/water interface. A broken line shows a linear extrapolation of the steep rise of the n-k isotherm. 

Mixing fatty acids with fatty bases can dissolve films as the resulting complexes become water-soluble however, in some cases the mixed Langmuir film is stabilized [128]. The application of an electric field to a mixed lipid monolayer can drive phase separation [129]. 

The first use of the SECM in a study of lateral mass transfer was reported by Unwin and Bard [79]. Several years later, the Unwin group studied the lateral mass transfer of a surfactant at the air-water (A-W) interface by analyzing transient current behavior [81]. The electroactive surfactant, A-octadecylferro-cenecarboxamide (CigFc0) was mixed with 1-octadecanol in a 1 1 ratio and spread onto water surface to form a Langmuir monolayer. A 25-pm diameter submarine tip (i.e., a Pt UME sealed in a U-shaped glass capillary with the conductive surface pointing upward) was placed 1-2 pm away from the A-W... 

The mixing behavior of 10-(perfluorohexyl)-decanol and DPPC in Langmuir monolayers has recently been reported, showing partial miscibility, especially at low surface pressure [67], 10-(perfluorohexyl)-Decanol was studied because it is a fluorinated analog of hexadecanol, which has been used in synthetic lung surfactant compositions. 

Compounds used to form Langmuir monolayers were stearic acid (>99.9%) and stearyl alcohol (>99.9%) purchased from Aldrich. Stearic acid known to bind with cadmium ions (CdCh, >99.9%, Aldrich) were mixed with stearyl alcohol at varying compositions from 100 0 to 50 30. Each solution was at the concentration of ImM in chloroform (>99%, Fluka). 

This term will be used for Langmuir monolayers containing additional molecules, adsorbed from the liquid substrate. Phenomenologically speaking, the monolayer is now mixed Langmuir-Gibbs. ... 

A related method that has been applied to Langmuir monolayers is sum-frequency generation (SFG) spectroscopy.The signal is generated by mixing an infrared wave of frequency (u,r with a visible wave of frequency CO to yield an output cosp. When co,r matches a vibrational frequency, there is a resonant enhancement of the output. The nonlinear polarization that governs the SFG process can be written... 

Li, L.Y., Chen, S.F., and Jiang, S.Y., Molecular-scale mixed alkanethiol monolayers of different terminal groups on Au(lll) by low-current scanning tunneling microscopy, Langmuir 19, 3266-3271, 2003. 

Penetration systems at the air-water interface in which a dissolved amphiphile (surfactant, protein) penetrates into a Langmuir monolayer are interesting models for a better understanding of various complex processes. Most of all, penetration systems can simulate properties of biological membranes typically comprised of lipids mixed with proteins. First penetration experiments have been described by Schulman and Hughes in 1935 [110]. In the... 

In a clever attempt to form Langmuir monolayers of pure Cgo> Metzger and collaborators prepared an amphiphilic derivative by a thermally reversible Diels-Alder reaction (Scheme 7) [99], The temporary introduction of the car-boxyhc acid functionality guarantees an efficient anchoring of the fullerene spheroid to the water layer. The monolayers could be successfully transferred onto sohd substrates to form LB monolayers and multilayers. Upon heating, the Diels-Alder adduct decomposes, giving back Cgo. Thus, the final film consists of mixed layers of pure Cgo and Cgo/adduct. 

When two people do not like each other they are said to "mix about as well as oil and water." One of the most familiar classifications in chemistry is one that differentiates hydrophilic ("water-loving") molecules (and parts of molecules) from "hydrophobic" ("water-fearing") molecules (and parts of molecules). The structures of Langmuir monolayer micelles, described in chapter 2, and cell membrane bilayers are often said to result from "hydrophobic bonding" of long hydrophobic hydrocarbon chains. 

Evans S.D., Sanassy P. and Uhnan A. 1994. Mixed alkanethiolate monolayers as substrates for studying the Langmuir deposition process. Thin Sohd Films, 243, 325-329. 

Sanassy P. and Evans S.D. 1993. Mixed alkanethiol monolayers on gold surfaces substrates for Langmuir-Blodgett film deposition, Langmuir, 9, 1024-1027. 

Langmuir and Langmuir-Blodgett (LB) films of neat titanyl(IV) phthalocyanine (TiOPc) and mixed (TiOPC)-arachidic acid (AA) films were studied by Del Cano et alP. The surface pressure-area isotherms (T-A) were recorded, and an unusual expansion of the surface area per molecule was detected for mixed TiOPc-AA Langmuir monolayers. The expansion is attributed to the TiOPc... 

In the case of the mixed organosilane monolayer prepared by Langmuir s method, it was shown that the (n-octadecyltrichlorosilane (OTS)/[2-(perfluorooctyl)ethyl] trichlorosilane (POETS)) mixed monolayer was in a phase-separated state whose domain and matrix phases were composed of the OTS and the POETS molecules, respectively.fi-6) In the cases of the (alkylsilane/fluoroalkylsilane) mixed monolayer with phase-separated structure, the method of precise structure control has been discussed. 

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