Electrostatic Self-Assembly of Oppositely Charged Copolymers and Surfactants: A Light, Neutron, and X-ray Scattering Study

Abstract

We report on the formation of colloidal complexes resulting from the electrostatic self-assembly of polyelectrolyte−neutral diblock copolymers and oppositely charged surfactant. The copolymers investigated are asymmetric and characterized by a large neutral block. Using light, neutron, and X-ray scattering experiments, we have shown that the colloidal complexes exhibit a core−shell microstructure. The core is described as a dense microphase of micelles connected by the polyelectrolyte blocks, whereas the shell is a diffuse brush made from the neutral chains. For all copolymer/surfactant systems, we show the existence of a critical charge ratio ZC (∼1) above which the formation of hierarchical structures takes place. Copolymers of different molecular weight and polyelectrolyte blocks have been studied in order to assess the analogy with another type of core−shell aggregates, the polymeric micelles made from amphiphilic copolymers. The present results indicate that the radius of the core depends essentially...