Critical Conditions for Binding of Dimethyldodecylamine Oxide Micelles to Polyanions of Variable Charge Density

The binding of N, N -dimethyldodecylamine oxide micelles to oppositely charged polyanions of variable charge density, namely sulfonated poly(vinyl alcohol) (PVAS) and random copolymers of 2-(acrylamido)-2-methylpropanesulfonate and acrylamide (P(AMPS-AAm)), was studied using turbidimetry, dynamic light scattering, and potentiometric titration. Complexation occurs at a well-defined critical pH corresponding to a critical micelle surface charge density σ c . The effects of ionic strength I on σ c and polyelectrolyte average structural charge density ξ conform to σ c ξ a ∼ κ b, where κ is the Debye−Hückel parameter proportional to I 1/2 . Taken along with previous studies, the results show that the exponent b for cylindrical micelles is larger than that for spherical micelles. The effects of ξ cannot be explained solely on the basis of average charge spacing but must also take into account the sequence distributions of charged residues.