Growth of Mixed Nonionic Micelles

Abstract

Static and quasielastic light-scattering measurements were utilized to investigate the shape, size, and polydispersity of mixed micelles composed of the nonionic surfactants dodecyl hexaoxyethylene glycol monoether (C12E6) and dodecyl octaoxyethylene glycol monoether (C12E8) in aqueous solutions. We determined the molecular weight and diffusion coefficient of these micelles and showed that they are rodlike. The average diffusion coefficient of the mixed micelles was measured at various total surfactant concentrations in the range between approximately 30 and 1000 times the critical micellar concentration of the surfactant mixture. Pure C12E6, pure C12E8, and three different mixtures of C12E6 and C12E8 were studied in the temperature range 10 °C ≤ T ≤ 55 °C. We found that the mixed micelles could be satisfactorally described as prolate ellipsoids with an average long axis which grows in size as the total surfactant concentration increases. The extent of this growth is more pronounced when the relative proportion of C12E6 in solution is increased or as the temperature approaches the boundary of phase transition into coexisting micelle-rich and micelle-poor phases. We propose a phenomenological model to quantitatively describe the linear growth of rodlike mixed micelles. Two parameters of this model which control the observed linear growth of the mixed C12E6 and C12E8 micelles were deduced from the experimental data and compared with the values predicted by a recently developed molecular−thermodynamic theory of mixed micellization.

Structure determination of micelle-like intermediates in amyloid β-protein fibril assembly by using small angle neutron scattering

“…The fact that the A␤ micelle-like intermediates in our experiments are elongated objects that do not change size with A␤ concentration has important consequences. Elongated, wormlike micelles are well known (10,17). However, the length of those micelles increases with concentration.…”

Conformations of Highly Charged Dendronized Polymers in Aqueous Solutions of Varying Ionic Strength

“…A rod like conformation of P2 molecules is highly probable owing to the four carboxylic groups in each repeating unit and low molar mass of P2. Assuming a rod like conformation [17] and a conformation of a prolate ellipsoid of revolution, [18] the hydrodynamic radius of individual macromolecules can be theoretically predicted. These predictions employ the formulae presented below.…”

A Conformational Change in the Human Major Histocompatibility Complex Protein HLA-DR1 Induced by Peptide Binding

“…Ten measurements were taken for each sample. The signal was processed by a Langley Fold model 1096 correlator, and data analysis was performed using a regularization procedure (36), modified for the analysis of the goniodyne autocorrelation function (37). The autocorrelation function was utilized to reconstruct the distribution of the scattering particles over diffusion coefficients from fluctuations in the scattering intensity of the protein solution.…”