COMPLEX-FORMATION BETWEEN POLY(OXYETHYLENE) AND SODIUM DODECYL-SULFATE MICELLES - LIGHT-SCATTERING, ELECTROPHORESIS, AND DIALYSIS EQUILIBRIUM STUDIES

The structure and behavior of polymer-micelle complexes formed in dilute solutions of poly(ethylene oxide) (PEO) and lithium dodecyl sulfate (LDS) in LiCl solution were studied by quasi-elastic light scattering, electrophoretic light scattering, static light scattering, and dialysis equilibrium, as a function of polymer molecular weight (M) and ionic strength (I). In 0.4 M LiCl, the diffusion coefficient of the LDS-saturated complex shows an exponential M dependence, i.e. D = kMv. The value of v = -0.55 is typical of nonionic flexible chain polymers (for PEO alone v = -0.52) in good solvents. The electrophoretic mobility, u, of the complex is nearly M-independent, similar to the behavior of polyelectrolytes. These results suggest an overall Gaussian distribution for the PEO-LDS complex, with sufficient chain expansion to yield free-draining behavior. The number of micelles bound per chain increases strongly with ionic strength, as does the electrophoretic mobility. This result can be interpreted on the basis of the contribution of uncharged bound polymer to the friction force per bound micelle. The present results support a micelle-polymer interaction mechanism which involves simultaneous binding of Li+ by both the micelle and the polymer.