Dielectric property micelle

The observation of slow, confined water motion in AOT reverse micelles is also supported by measured dielectric relaxation of the water pool. Using terahertz time-domain spectroscopy, the dielectric properties of water in the reverse micelles have been investigated by Mittleman et al. [36]. They found that both the time scale and amplitude of the relaxation was smaller than those of bulk water. They attributed these results to the reduction of long-range collective motion due to the confinement of the water in the nanometer-sized micelles. These results suggested that free water motion in the reverse micelles are not equivalent to bulk solvation dynamics. 

Several papers compare the properties of sulfobetaine (meth)acrylic polymers. NMR spectra and solution properties of 23a and 23b [59,60] are correlated with data from the corresponding polycarbobetaines [26]. The photophysical and solution properties of pyrene-labeled 23c were studied in terms of fluorescence emission. Addition of surfactants induces the formation of mixed micelles in aqueous solution [61]. Excluded volume effects of the unlabeled polymer were measured by light scattering [62], its adsorption on silica was studied by adsorbance measurement and ellipsometry [62,63], and the electrostimulated shift of the precipitation temperature was followed at various electric held intensities [64]. Polysulfobetaines may accelerate interionic reactions, e.g., oxidation of ferrocyanide by persulfate [65]. The thermal and dielectric properties of polysulfobetaines 23d were investigated. The flexible lateral chain of the polymers decreased Tg, for which a linear relationship with the number of C atoms was shown [66,67]. 

Apart from the type of phospholipids the formation of phospholipid structures such as bilayers, micelles or inverted micelles are directly dependent on the degree of hydration, the hydrophobic forces on the tatty acyl chains, and the electrostatic forces that are present on the polar head group region of the bilayer. The properties of the aqueous medium (pH, ionic strength, dielectric properties) are factors that influence the type of phospholipid structures. 

Effects of sodium dodecyl sulfate (SDS) on the electromagnetic properties of PANI/y-Fe Oj nanocomposites, prepared by using the reverse micelle polymerization where aniline, ferrous/ferric salts, and SDS act as monomer, precursor of y-Fe O and surfactant, respectively, were investigated by Hsieh et al. [188] (Figure 2.18). It was showed that the y-Fe O content and particle size in the PANI/y-Fe Oj nanocomposites decreased, crystallinity, conductivity, and dielectric properties (i.e., permittivity and... 

Related works that deserve attention are those devoted to the dielectric properties of ternary micellar solutions build up with water, a hydrocarbon and either AY or AOT aerosols (25,54). For instance, Elcke and Shepherd (25) suggested that the non-linear variations of the dielectric relaxation increment and the sudden increase in conductivity observed upon increasing the water content in water/AY/benzene systems could be interpreted in terms of association process and micelle conformational change. 

In a word, the conductivity of inverse micelle systems is essentially controlled by ionic transportation under an electric field, and the ions are the charged inverse micelles. The electric-field-induced charging mechanism may well describe how inverse micelles are charged and well explain the observed experimental phenomena to date. Since the charged micelles arc major components, the dielectric property of the inverse micelle systems may simply controlled by the electrode polarization process, which will be described in next section. 

A Inverse micelle size calculated from the dielectric property... 

The effects of the intramicellar confinement of polar and amphiphilic species in nanoscopic domains dispersed in an apolar solvent on their physicochemical properties (electronic structure, density, dielectric constant, phase diagram, reactivity, etc.) have received considerable attention [51,52]. hi particular, the properties of water confined in reversed micelles have been widely investigated, since it simulates water hydrating enzymes or encapsulated in biological environments [13,23,53-59]. 

The adempts to rationalize GrifHn s HLB scale from a physicochemical point of view were made in a number of studies. Various correlations were shown to exist between the HLB numbers and the chemical structure or molecular composition of the siufactants. Correlations were also fotmd between the HLB number and physicochemical properties of surfactants and their solutions, for example, stffface and interfacial tension, solubility, and heat of solution, spreading and distribution coefficient, dielectric permittivity of the surfactant, cloud point and phase inversion point, critical micelle concenlration, foaminess, etc. These studies are reviewed in Ref. 262. However, the correlations found are not generally applicable moreover, the concept of the additivity of HLB numbers as such for mixtures of surfactants or oils cannot be proven expermentally when the surfactant characteristics are varied over a wider range (265). 

The changes involved in surfactant aggregation in nonaqueous solvents must differ considerably from those already discussed for water-based systems. The orientation of the surfactant relative to the bulk solvent will be the opposite to that in water (hence the term reversed micelle). In addition, the micelle, regardless of the nature of the surfactant, will be un-ionized in solvents of low dielectric constant, and so will have no significant electrical properties relative to the bulk solvent, although electrostatic interactions will play an important role in the aggregation process, but in an opposite sense to that in aqueous solution. 

Observations have also been made on the properties of the bound and bulk water molecules. Thus, a two-state model [142, 143] has been proposed for the water molecules in the core of the reverse micelle a very viscous water which is close to the interface, and water in the center of the pool which has properties similar to those of bulk water. This is specially evident when the [H20]/[A0T] ratio is increased beyond a threshold value [143], leading to the formation of a bulky structured water plus bulk-like water variation in dielectric constant is also noted in such cases. It has been noted [143] that the effective dielectric constant at the AOT/n-heptane interface increased with w 2.3 at w = 0, increasing to 9 at w 10, finally reaching a plateau at w 12. In case of AOT reverse micelles, a discontinuity of some physical properties has been noted at a w value of about 12. It has further been indicated that at low values of w, hydration of AOT head-groups and the counterions is important, so a bulky structured water can be visualized on the other hand, at high values of w, the aqueous core becomes bulklike [143]. 

The properties of ionic polymers in nonaqueous media have only recently become the subject of systematic studies. In solvents of low dielectric constant, salt groups resist dissociation and are poorly solvated. Thus, ionic moieties promote intra- and inter-polymer association in organic solvents. The tendency of ionic groups to aggregate or cluster resembles the coalescence of such groups in reversed micelles. Similar considerations underly the formation of ionic "cross-links" that modify the behavior of ionomers in the solid state. Solutions of polyions in nonaqueous media thus provide systems in which a powerful array of experimental techniques can be used to probe phenomena that are important to the bulk properties of a commercially important group of materials. The article by Teyssie and Varoqui in Part IV describe significant explorations in this novel field. 

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