POLYELECTROLYTES AND OPPOSITELY CHARGED SURFACTANTS IN ORGANIC-SOLVENTS - FROM REVERSED MICELLES TO SOLUBLE POLYMER-SURFACTANT COMPLEXES

This work studies aggregates formed by poly(N-ethyl-4-vinylpyridinium bromide) (PEVP) and oppositely charged sodium bis(2-ethylhexyl) sulfos uccinate (Aerosol OT) molecules in aliphatic hydrocarbon solvents (oct ane and hexane). It demonstrates that various polycation-surfactant st ructures are formed during PEVP solubilization in Aerosol OT solutions depending on the amount of water added to the system. At high degrees of hydration PVPE incorporates in the water pool of a reversed micell e formed by the surfactant where the polycation chain is substantially condensed. According to the light scattering and ultracentrifugation data, the incorporation of the polycation affects Little the size of t he reversed micelles. Under these conditions the water pools of PEVP-c ontaining micelles may also incorporate other macromolecules (e.g., bo vine serum albumin) simultaneously with the polycation. At the critica l degree of hydration PEVP represents a swollen globule compressed by the micellar matrix. The density of the polycation in such globules eq uals about 0.5 g/cm(3) and about 50% of the globule volume is occupied by water molecules. Below the critical degree of hydration the polyca tion and the surfactant form a stoichiometric polymer-surfactant compl ex soluble in aliphatic hydrocarbons. The dimensions of such complexes are significantly higher than those of the initial empty reversed mic elles, and they apparently represent ''comblike'' structures in which the Aerosol OT head groups are electrostatically bound with the charge d units of PEVP, whereas the hydrophobic tails of the surfactant, ''gr afted'' to the polycation, are exposed to the bulk solvent.