Coexistence of Crew-Cut and Starlike Spherical Micelles Composed of Copolymers with an Annealed Polyelectrolyte Block

Abstract

The self-assembly of block copolymer AmBn into spherical micelles is analyzed using a numerical self-consistent-field theory. A is the hydrophilic annealed polyacid and B the hydrophobic part. The degree of polymerization for the polar moiety is fixed (m = 100), whereas that of the tail is varied (n = 100, 200, and 300). The charge in the annealed A block depends on both the pH and the added 1:1 electrolyte concentration φs. Beyond the cmc, the diblock copolymers form either low aggregation number starlike or large aggregation number crew-cut micelles. A nonmonotonic behavior of the micellar properties as a function of φs for fixed pH is found. For starlike micelles, the scaling of the aggregation number Nagg with φs is in fair agreement with analytical predictions, i.e., Nagg ∼ φs0.7-0.9. For the core radius, we find that Rcore ∼ φs0.24-0.3, and for the corona thickness Tcorona ∼ φs-0.08. For crew-cut micelles, the scaling exponents deviate significantly from analytical predictions. Upon increasing pH, a...