Critical conditions for binding of dimethyldodecylamine oxide micelles to polyanions of variable charge density

The binding of N,N-dimethyldodecylamine oxide micelles to oppositely charge d polyanions of variable charge density, namely sulfonated poly(vinyl alcoh ol) (PVAS) and random copolymers of 2-(acrylamido)-2-methylpropanesulfonate and acrylamide (P(AMPS-AAm)), was studied using turbidimetry, dynamic ligh t scattering, and potentiometric titration. Complexation occurs at a well-d efined critical pH corresponding to a critical micelle surface charge densi ty sigma (c). The effects of ionic strength I on or, and polyelectrolyte av erage 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 alon g with previous studies, the results show that the exponent b for cylindric al micelles is larger than that for spherical micelles. The effects of cann ot be explained solely on the basis of average charge spacing but must also take into account the sequence distributions of charged residues.