Diblock copolymers in a selective solvent often assemble into spherical micelles. These micelles demonstrate long range order at moderate polymer concentrations. We explore the nature of the disorder-order transition in micellar suspensions through small angle x-ray diffraction studies. The phase behavior includes body-centered cubic (bcc) and face-centered cubic (fcc) lattices. We present the first phase diagram for block copolymer micelles to include both bcc and fcc structures and characterize the lattice selection by a ratio of coronal layer thickness to core radius.

• Received 23 June 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.2102