| Abstrakt: |
The utility of using the Zimm plot and its analogs, the Debye and Berry plots, as a sensitive means of determining the degree of polydispersity present in solutions of surfactant aggregates such as vesicles or micelles is conclusively demonstrated. These methods of interpreting the excess scattered light intensity due to the surfactant aggregates lead to the determination of the weight-average molecular weight (Mw) and z-average mean square radius (z), or radius of gyration, of the surfactant aggregates. These two parameters are very sensitive to any polydispersity which is present in the aggregate solution, since these two experimentally determined quantities represent different moments of the aggregate size distribution. For a given geometric model, apparent surfactant aggregate structural parameters, such as the radius and wall thickness in the case of surfactant vesicles, can be calculated under the assumption of monodisperse aggregates from z and Mw determined from a Zimm or Debye analysis of static light scattering spectra. For vesicles whose polydispersity is described by a Schulz distribution it is shown that the calculated apparent wall thickness and dispersion polydispersity are strongly correlated, thereby demonstrating the utility of this approach for determining vesicle dispersion polydispersity. Analogous approaches can be used to determine the degree of polydispersity present in surfactant solutions containing spherical, rod-like, or disk-like micelles. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
