Search

Structures formed by self-assembly of α- and β-1-n-octyl-D-glucopyranoside and β-1-n-dodecyl-D-maltoside in water depend upon the configuration at the anomeric center. The β-anomers form aggregates of size comparable to normal ionic micelles, while the α-glucoside is sparingly soluble in water and forms very large, nonspherical assemblies. This contrasting behavior suggests that the head group configuration controls its orientation to the apolar residue and, consequently, the packing of monomers in self-assemblies.The β-anome the latter is evidence of its strong interaction with micellized β-maltoside.

The light-scattering techniques of intensity angular dissymmetry and photon correlation spectroscopy are used to determine the static correlation length, osmotic compressibility, and diffusivity of an oil-in-water microemulsion. The observed temperature dependence of these quantities near a phase separation point qualitatively resembles the critical behavior found for simple fluids and binary mixtures, but with substantially larger values of the critical exponents $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\nu}}$ and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\gamma}}$.

Using the method of cumulants, we investigate the distribution of diffusion coefficients in polydisperse systems. We consider the intensity weighting for distributions of spherical particles having the same polarizability. Results of computer simulations are presented for a variety of polydisperse situations. Also, comparisons are made between predicted and measure results for mixtures of Dow latex spheres.

We present calculations for the mean aggregation number and radius of gyration versus the mean hydrodynamic radius for polydisperse distributions of SDS micelles. We also present new measured values for the hydrodynamic radius. These results carry significant implications for the average number of monomers per micelle and for the micellar shape.

Using the method of dynamic light scattering we have measured the diffusion coefficients D of cetyltrimethylammonium hydroxide (CTAOH) micelles as a function of CTAOH and NaOH concentrations at 25°C for 0.01 ≤ [CTAOH] ≤ 0.05 M and 0.02 ≤ [NaOH] ≤ 0.5 M. Substantial enhancements in the diffusivity were observed at low [NaOH] due to the presence of strong intermicellar electrostatic repulsions. We obtained good theoretical fits to the D versus [CTAOH], [NaOH] data over the range 0.01 ≤ [NaOH] ≤ 0.5 M using linear interaction theory (including both thermodynamic and hydrodynamic corrections to D ) with a DLVO-type pair interaction potential. From these fits we obtained estimates of the mean micellar hydrodynamic radius, R h ∼ 23.4 A, and the micellar fractional ionization, α ∼ 0.5.

The micellar diffusivity, measured by quasielastic light scattering, is described by a simple phenomenological expression for a variety of surfactants over a range of surfactant concentrations and temperatures at low salt concentration where electrostatic interactions dominate. This universal expression contains the low order perturbations to the micellar diffusivity in the absence of interactions. The dominant correction scales with the ratio of surfactant to salt concentrations and results from repulsive electrostatic interactions, screened by the added salt ions. By fitting experimental data to this expression, we obtain the Stokes–Einstein micellar radius and a relative measure of the micellar ionization fraction.

The diffusion coefficient and correlation radius associated with the droplet particles in oil-in-water microemulsions (CTAB, octane, butanol, NaBr and water) were determined by dynamic light scattering- Unlike the case of CTAB micelles, there is a maximum in the correlation radius versus temperature plot.