COMPLEX-FORMATION BETWEEN POLYELECTROLYTE AND OPPOSITELY CHARGED MIXED MICELLES - STATIC AND DYNAMIC LIGHT-SCATTERING STUDY OF THE EFFECT OF POLYELECTROLYTE MOLECULAR-WEIGHT AND CONCENTRATION

Dynamic light scattering, static light scattering, and turbidimetry we re used to investigate the effect of polyelectrolyte molecular weight and concentration on complex formation between a strong polyelectrolyt e, poly(dimethyldiallylammonium chloride) (PDMDAAC), and oppositely ch arged mixed micelles of Triton X-100 (TX100) and sodium dodecyl sulfat e (SDS). The hydrodynamic radius (R(h)) of the complexes is about twic e those of the PDMDAAC from which they are formed, while the radius of gyration (R(g)) of the complexes remains essentially unchanged. This suggests that the complex formed is compact. With increasing polyelect rolyte concentration, intrapolymer complexes transform to interpolymer complexes. The interpolymer complexes are not stable and in time phas e separate (coacervate). Although the polyelectrolyte molecular weight has only a small effect on the structure of the complex in the intrap olymer complex region, the intra- to interpolymer complex transition d epends strongly upon the molecular weight of the polyelectrolyte. The polyelectrolyte concentration at which the transition occurs decreases with increasing polyelectrolyte molecular weight. If the polyelectrol yte molecular weight is low enough, this sharp transition is not obser ved, and no associative phase separation is observed.