COMPLEX-FORMATION BETWEEN SODIUM DODECYL-SULFATE AND POLY(4-VINYLPYRIDINE N-OXIDE)

The interaction of poly(4-vinylpyridine-N-oxide)(PVPNO) with sodium dodecyl sulfate in aqueous solutions was examined using surface tension, turbidimetry, and light scattering (quasielastic, electrophoretic, and total intensity light scattering). Surface tension measurements show that the polymer begins to interact with SDS at a concentration below the critical micelle concentration (cmc), in a manner similar to the behavior of other nonionic polymer-surfactant systems (e.g., PEO-SDS). Turbidimetric and quasielastic light scattering (QELS) studies at SDS concentrations much above the cmc clearly reveal the formation of a soluble polymer-micelle complex. On the other hand, phase separation, similar to that observed for polyelectrolyte-oppositely charged micellar systems, occurs at low pH, presumably as a consequence of protonation of the polymer to form a polycation. Total intensity data show saturation of the polymer with bound micelles at high SDS concentration, while QELS measurements clearly reveal two peaks: one corresponding to free micelles and the other to the complex. Quasielastic and electrophoretic light scattering measurements were carried out on mixtures of SDS and PVPNO, SDS and PEG, or SDS and both polymers. These indicate that the binding of SDS micelles to PVPNO in 0.10 M NaCl is not as strong as the binding to PEG.