Micelle size and shape

With the development of new instrumental techniques, much new information on the size and shape of aqueous micelles has become available. The inceptive description of the micelle as a spherical agglomerate of 20-100 monomers, 12-30 in radius (JJ, with a liquid hydrocarbon interior, has been considerably refined in recent years by spectroscopic (e.g. nmr, fluorescence decay, quasielastic light-scattering), hydrodynamic (e.g. viscometry, centrifugation) and classical light-scattering and osmometry studies. From these investigations have developed plausible descriptions of the thermodynamic and kinetic states of micellar micro-environments, as well as an appreciation of the plurality of micelle size and shape. 

Hayashi S, Ikeda S. Micelle size and shape of sodium dodecyl-suUate in concentrated NaCl solutions. J Phys Chem 1980 84 744-751. 

Although a number of infrared bands can be used to establish that a micellar shape change has occurred, it is difficult to determine the actual shape unambiguously from the spectroscopic data alone. We therefore make use of micelle aggregation numbers and solution rheological properties, which depend on micelle size and shape, for correlation with the structural information (packing) provided by the FTIR spectra. 

CH1 Chaibundit, C., Ricardo, N.M.P.S., Crothers, M., and Booth, C., Micellization of diblock (oxyethylene/oxybutylene) copolymer EuBg in aqueous solution. Micelle size and shape. Drag solubilization, Langmuir, 18, 4277, 2002. 

In summary, NMR studies can deal with a wide range of problems in surfactant science. These include, e.g., molecular transport, phase diagrams, phase structure, self-association, micelle size and shape, counterion binding and hydration, solubilization, and polymer-micelle interactions. NMR is fruitfully applied to isotropic or liquid crystalline bulk phases, to dispersions (vesicles, emulsions, etc.), to polymer-surfactant mixtures, and to surfactant molecules at solid surfaces. In all cases NMR can provide information on molecular interactions and dynamics as well as on microstructure. 

M. Nyd6n, Measuring micelle size and shape, in Handbook of Applied Surface and Colloid... 

G. Bile Salt Micelle Size and Shape — Effects of Structure, Concentration, Counterion, pH, Temperature, Urea, and Other Solvents... 

The assembly of amphiphilic block copolymers to generate discrete nanoscale structures is primarily driven by the hydrophobic effect, with micelle size and shape governed by a set of basic principles rooted in surfactant phase-separation behavior [22-28]. Important parameters that control the size of micelles are the degree of polymerization of the polymer blocks and the Flory-Huggins interaction parameter [28]. 

To start with, NMR is a very powerful tool for the study of surface and colloid chemistry in general and several good reviews on this subject have been produced (1-5). As far as micelle size and shape are concerned, two main experiments prevail in the literature, namely NMR relaxation and self-diffusion measurements. The technique of NMR self-diffusion is a relative tool for the study of micellar size and shape since it uses the Stokes-Einstein relationship (or modifications to it) to... 

VI. PROPERTIES OF MICELLES OF GEMINI SURFACTANTS A. Micelle Size and Shape... 

It is most likely that none of the preservative combinations used had exactly the same locus or are solubilized by the same mechanism, so that simple competition between the solubilizates in the micelle is unlikely alternatively the interaction of some of the preservatives with the micelle (or monomers) leads to perturbations of micelle size and shape such that binding sites are altered in their capacity to accept solubilizate molecules. 

Like surfactants, block copolymers form micelles above a critical concentration. The critical micelle concentration can be located by a variety of techniques [112], the most commonly used being surface tensiometry where the cmc is located as the point at which the surface tension becomes essentially independent of concentration. The primary methods to determine micelle size and shape are light scattering and small-angle X-ray and neutron scattering. The thermodynamic radius (from the thermodynamic volume, which is one eighth... 

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