Micellization determination

Investigation of water motion in AOT reverse micelles determining the solvent correlation function, C i), was first reported by Sarkar et al. [29]. They obtained time-resolved fluorescence measurements of C480 in an AOT reverse micellar solution with time resolution of > 50 ps and observed solvent relaxation rates with time constants ranging from 1.7 to 12 ns. They also attributed these dynamical changes to relaxation processes of water molecules in various environments of the water pool. In a similar study investigating the deuterium isotope effect on solvent motion in AOT reverse micelles. Das et al. [37] reported that the solvation dynamics of D2O is 1.5 times slower than H2O motion. 

Pervushin KV, Orekhov V, Popov AI, Musina L, Arseniev AS (1994) Three-dimensional structure of (l-71)bacterioopsin solubilized in methanol/chloroform and SDS micelles determined by 15N-1H heteronuclear NMR spectroscopy. Eur J Biochem 219 571-583... 

Let us recall the micellar aqueous system, as this procedure is actually the basic one. The chemistry is based on fatty acids, that build micelles in higher pH ranges and vesicles at pH c. 8.0-8.5 (Hargreaves and Deamer, 1978a). The interest in fatty acids lies also in the fact that they are considered possible candidates for the first prebiotic membranes, as will be seen later on. The experimental apparatus is particularly simple, also a reminder of a possible prebiotic situation the water-insoluble ethyl caprylate is overlaid on an aqueous alkaline solution, so that at the macroscopic interphase there is an hydrolysis reaction that produces caprylate ions. The reaction is very slow, as shown in Figure 7.15, but eventually the critical micelle concentration (cmc) is reached in solution, and thus the first caprylate micelles are formed. Aqueous micelles can actually be seen as lipophylic spherical surfaces, to which the lipophylic ethyl caprylate (EC) avidly binds. The efficient molecular dispersion of EC on the micellar surface speeds up its hydrolysis, (a kind of physical micellar catalysis) and caprylate ions are rapidly formed. This results in the formation of more micelles. However, more micelles determine more binding of the water-insoluble EC, with the formation of more and more micelles a typical autocatalytic behavior. The increase in micelle population was directly monitored by fluorescence quenching techniques, as already used in the case of the... 

Mack (58, 59) points out that asphaltenes from different sources in the same petro-lenes give mixtures of approximately the same rheological type, but sols of the same asphaltenes in different petrolenes differ in flow behavior. Those in aromatic petrolenes show viscous behavior and presumably approach true solution. Those in paraffinic media show complex flow and are considered to be true colloidal systems. Pfeiffer and associates (91) consider that degree of peptization of asphaltene micelles determines the flow behavior. Thus, a low concentration of asphaltenes well peptized by aromatic petrolenes leads to purely viscous flow. High concentrations of asphaltenes and petrolenes of low aromatic content result in gel-type asphalts. All shades of flow behavior between these extremes are observed. 

Zhang, R., PA. Marone, P. Thiyagarajan, andD. M.Tiede. 1999. Structure and molecular uctuatBbk lof /3-D-glucopyranoside micelles determined by x-ray and neutron scattfeangmuirl 5 7510-7519. 

The effect of electrolyte addition to oscillatory behaviour has also been considered in [235]. The disappearance of structural transition upon electrolyte addition was attributed to its electrostatic origin. The viscosity of the film did not differ much from that of the bulk solution in the case when micelles determined the structuring of the amphiphile surfactant molecules. It is worth to note that the length scale of the oscillations was large, about 10 nm and even reached about 50 nm. 

The amount, flexibility, and strength of the threadlike micelles determine the temperature range, critical wall-shear stress, and maximum DR ability of surfactant solutions. 

Since the dynamics of the twisted intramolecular charge transfer (TICT) process is very sensitive to the polarity of the medium, the local polarity of an organized medium may also be determined from the rate of the HCT process. For TNS, which is nearly nonfluorescent in water ((j)f = 10 and Xf = 60 ps), the emission quantum yield and lifetime increases nearly 50 times on binding to cyclodextrins and more than 500 times on binding to a neutral micelle, TX -100 [86]. Such a dramatic increase in the emission intensity and lifetime arises because of the marked reduction of the nonradiative HCT process inside the less polar microenvironment of the cyclodextrins and the micelle. Determination of the micropolarities of various organized assemblies using TICT probes has been surveyed quite extensively in several recent reviews [5b-d,f,86]. Therefore, in this chapter we will focus only on some selected works not covered in the earlier reviews. 

Javet, J., Zdunek, J., Damberg, P, and Gaslund, A. (1997). Three-dimensional structure and position of porcine motilin in sodium dodecyl sulfate micelles determined by H-NMR. Biochemistry 36,8153-8163. 

Lipfert J, Columbus L, Chu VB, Lesley SA, Doniach S (2007) Size and shape of detergent micelles determined by small-angle X-ray scattering. J Phys Chem B 111 12427-12438... 

Lindberg M, Graslund A (2001) The position of the cell penetrating peptide penetratin in SDS micelles determined by NMR. FEBS Lett 497 39 14... 

Figure 20.13. The viscosity of a solution of a hydrophobically modified water-soluble polymer and a surfactant compared to the concentration of micelles (determined by fluorescence quenching). The viscosity (filled circles) has a maximum when the micelle concentration starts to increase. The system illustrated is that of hydroxyethyl cellulose (1 wt%) and sodium dodecyl sulfate (SDS). (S. Nilsson, Ph. D. Thesis, Lund University, Sweden, 1999)...

Direct micelles contain lyophilic component of surface-active substance, whereas the reverse micelles contain lyophobic one. The miceUes can be formed in the presence and absence of water. In the case of reverse miceUes, for instance, in the hydrocarbon medium, water is easily solubilized, forming a water pool . Its size is characterized by the ratio of the water and surfactant volumes. Thus, a limited amount of water inside the micelle determines the kinetics and thermodynamics of the nanoparticles formation in a small micro/nanoreactor volume. 

M. Kotlarchyk, J. S. Huang and S. H. Chen, Structure of AOT reverse micelles determined by... 

Menger, E.M., Keiper, J.S., Mbadugha, B.N.A., Caran, K.L., Romsted, L.S. Interfacial composition of gemini surfactant micelles determined by chemical trapping. Langmuir 2000,16(23), 9095-9098. 

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