Higher order association in polyelectrolyte-micelle complexes

Abstract

Strong polyelectrolytes form Coulombic complexes with oppositely charged micelles. In the case of strong polycations with anionic/nonionic mixed micelles, the interaction is primarily influenced by the composition of the mixed micelle (i.e., the mole fraction of anionic surfactant, Y) and the ionic strength, I. For poly-(dimethyldiallylammonium chloride) in the presence of sodium dodecyl sulfate/Triton X-100 mixed micelles, there is a range of Y and I in which soluble complexes are formed. The current report focuses on the structure of these complexes. Turbidimetric measurements, coupled with dynamic and static light-scattering results, suggest dramatic changes in the dimensions of the complex upon conjoint increase of I and V or increase in temperature. At normal ambient temperature, these changes occur abruptly in the ionic strength range 0.75 < I < 0.80 M; at a fixed ionic strength of 0.40 M, they occur in the temperature range 37-40°C. The foregoing conditions also correspond to the regimes of significant spherocylindrical growth of the mixed micelles. The increase in micelle dimensions appears to lead to a transition from intrapolymer complexes, in which several micelles are bound by a single polymer chain, to interpolymer association, in which many polymer chains are involved in a higher order aggregate. © 1990 American Chemical Society.