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 sigma (c). The effects of ionic strength I on or, and polyelectrolyte average structural charge density xi conform to sigma (c)xi (a) - kappa (b), where kappa is the Debye-Huckel 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 cannot be explained solely on the basis of average charge spacing but must also take into account the sequence distributions of charged residues.