Ordering, surfactants

In the latter the surfactant monolayer (in oil and water mixture) or bilayer (in water only) forms a periodic surface. A periodic surface is one that repeats itself under a unit translation in one, two, or three coordinate directions similarly to the periodic arrangement of atoms in regular crystals. It is still not clear, however, whether the transition between the bicontinuous microemulsion and the ordered bicontinuous cubic phases occurs in nature. When the volume fractions of oil and water are equal, one finds the cubic phases in a narrow window of surfactant concentration around 0.5 weight fraction. However, it is not known whether these phases are bicontinuous. No experimental evidence has been published that there exist bicontinuous cubic phases with the ordered surfactant monolayer, rather than bilayer, forming the periodic surface. 

Czuryszkiewicz T, Rosenholm J, Kleitz F, Linden M (2002) Synthesis and characterization of mesoscopically ordered surfactant/cosurfactant templated metal oxides. Impact of Zeolites and Other Porous Materials on the New Technologies at the Beginning of the New Millennium, Book Series Studies in Surface Science and Catalysis, Pts A and B 142 1117-1124... 

At higher concentrations of sinks, one might also expect shape transitions to ordered surfactant phases of microemulsion. 

Figure 13.5 (a) Ordered surfactant structures in aqueous solution, (b) Detail of a spherical anionic micelle with counter-cations. 

Surfactant propagation in the reservoirs has been modeled (44, 45) by allowing for surfactant adsorption, oil partitioning, and first-order surfactant decomposition all of these variables are functions of temperature. The foam mobility reduction is taken into account by reducing the gas relative permeability as follows ... 

It has been foimd that the n/i ratio is significantly determined by the intensity of agitation [2, 5], and this was conjectured to be related to stability of the ordered assemblies of surfactant hydrophobic ends at the liquid-liquid interface. Violent disturbance of the interface and a less orderly surfactant arrangement make possible more diversified steric routes of hydroformylation of linear olefin molecules. This relationship of the n/i ratio with the intensity of agitation has not been elucidated in a quantitative and mechanistic sense so far. 

Gibbs and Insoluble Monolayers The adsorption of surfactant molecules at the surface of a liquid can be so strong that a monomolecular film (Gibbs monolayer) of unidirectionally ordered surfactants is formed (Fig. 5). Since the decrease in surface tension is directly related to the surface excess adsorption of the surfactant by the Gibbs adsorption equation (Eq. 6), the formation of the Gibbs mono-layer can be monitored by decrease of the surface tension. The maximum number of molecules filling a given area depends upon the area occupied by each molecule. 

This review shows that stable, ordered surfactant films can facilitate electron exchange between proteins and elec-... 

Yang, J. Y., Kim, D. H., Hendricks, J. L., et al. (2005) Ordered surfactant-templated poly(3,4-ethylenedioxythiophene) (pedot) conducting polymer on microfabricated neural probes. Acta Biomaterialia 1, 125-36. 

By the end of the 1980s, it was clear that direct electrochemical observation of the redox chemistry of proteins required control of electrode surface structure and minimization of surface contamination [1-3], In this chapter, we discuss several strategies that combine these critical features with stable immobilization of native proteins in films on electrodes. In Section II, we discuss ordered surfactant films that provide biomembranelike environments for electrochemistry. In Section III, studies on polyion-protein films prepared by casting and grown layer by layer are snmmarized. Section IV presents studies on prototype bioreactors that make nse of electrode-driven enzymelike catalysis. Section V speculates about the future. 

Despite their potential importance, there are few spectroscopic studies of polymerizable surfactants. The only well-characterized polymerized surfactants are the polydiacetylenic fatty acids. The polymerization mechanism (1,4 addition) was only recently discovered as a result of studies on crystals of non-surfactant monomers which become brightly colored on polymerization [1], indicating the formation of polymer concurrent with a solid-solid phase transition. Several groups, particularly that of Ringsdorf, have pioneered the study of polydiacetylenic fatty acids [2-5]. A significant amount of spectroscopic work has been done on non-surfactant polydiacetylenes [6-9]. In addition, Lando and co-workers have used electron diffraction from mono- and bilayers of fatty acids to establish the conformation of the diacetylene backbone chains in this ordered surfactant system [10,11], and others have performed Raman spectroscopy on Langmuir-Blodgett films of similar surfactants [12]. This provides one with a powerful "basis set" of information from which to study other polydiacetylenic systems. 

Figure 6 Schematic diagram of (a) hexagonal phase of aligned, ordered rod-like micelles, and (b) lamellar phase of aligned, ordered surfactant bilayers.

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