No abstract

We have performed a series of small-angle neutron scattering (SANS) and static light scattering (SLS) experiments with dilute and semidilute solutions of polymer-like micelles formed by C16E6 in D2O at two different temperatures (T = 26 °C, 35 °C). The local structure has been investigated by applying indirect Fourier transformation and square-root deconvolution techniques. We demonstrate that the micelles maintain their locally cylindrical structure in this temperature regime despite the significant change in the spontaneous curvature of the surfactant. Detailed information on the micellar flexibility has been obtained from the SANS data by applying a nonlinear least-squares fitting procedure based upon a numerical expression for the single-chain scattering function of a worm-like chain with excluded volume effects. Particular attention has been given to the determination of quantitative numbers for the “intrinsic” persistence length as well as for the contribution from electrostatic interactions upon the addition of a small fraction of an ionic surfactant. The results have been compared with predictions from theoretical models for polyelectrolytes.

We report a small-angle neutron scattering (SANS) study of the cross-section structure of polymer-like lecithin reverse micelles in deuterated cyclohexane. We demonstrate that the application of the indirect Fourier transformation and square-root deconvolution methods to data from SANS measurements with cylindrical polymer-like micelles allows for a direct verification of the previously postulated geometrical model of flexible tubular structures with a well defined water core and a surfactant shell. By combining contrast variation experiments and data analysis performed on an absolute scale, we quantitatively deduce information on properties such as the extension of the aqueous core and the degree of water penetration into the headgroup and solvent penetration into the tail region.

The thermodynamics of the L3 (sponge) phase is investigated within the flexible surface model. The well-established leading-order 4l~scaling for the free energy density (where 4l is the surfactant volume fraction) requires modification in order to describe the narrow character of the phase and the observed sequence of phase transitions.