Study on the interaction between polyelectrolytes and oppositely charged ionic surfactants. Solubilized state of the complexes in the postprecipitation region

The effects of polymer charge and surfactant composition were examined on the complex-precipitation (CP) and phase-separation (PS) regions for cationic cellulose (CC), sodium poly(oxyethylene laurylsulfate) and lauroylamidopropyl-N,N-dimethylammonioacetate and Na₂SO₄. The solubilized state of the complexes was studied by light scattering in the one-phase, 1φ, solution in the postprecipitation region. The cationic charge on the CC and the anionic charge on the surfactant greatly affected the CP and PS regions, to change the domain of the 1φ solution. The relative scattering intensity of the complex, ΔI _complex , was high near the CP region and decreased with increasing surfactant and salt concentrations in the 1φ solution. The presence of solubilized complexes of polymers cross-linked with surfactant micelles was suggested near the CP region. The cross-linking of the complexes decreased with increasing surfactant and salt concentrations, producing increased micelle binding and charge shielding. The shrinkage of the complexes was considered to bring about the boundary on which ΔI _complex is equal to the relative scattering intensity of polymer alone in the 1φ solutions. Separation of the complexes and the transition of the solution into the PS region were suggested at high concentrations over the boundary. Received: 30 September 2000 Accepted: 7 May 2001