Starting from a microscopic lattice model, we investigate clustering, micellization, and micelle ordering in semidilute solutions of $AB$ diblock copolymers in a selective solvent. To bridge the gap in length scales, from monomers to ordered micellar structures, we implement a two-step coarse-graining strategy, whereby the $AB$ copolymers are mapped onto ultrasoft dumbells with monomer-averaged effective interactions between the centers of mass of the blocks. Monte Carlo simulations of this coarse-grained model yield clear-cut evidence for self-assembly into micelles with a mean aggregation number $n\simeq 100$ beyond a critical concentration. At a slightly higher concentration the micelles spontaneously undergo a disorder-order transition to a cubic phase. We determine the effective potential between these micelles from first principles.

• Received 18 January 2006

DOI:https://doi.org/10.1103/PhysRevLett.96.128302