Diblock copolymer micelles in a dilute solution

We performed theor. and exptl. investigations of dil. solns. of micelles of neutral amorphous diblock copolymers in selective solvents. The ranges of thermodn. stability of spherical, cylindrical, and lamellar morphologies along with the equil. sizes and aggregation nos. of micelles are calcd. and measured. For high mol. wt. copolymers it is shown that the sphere-to-cylinder transition as well as pptn. of the micelles assocd. with cylinder-to-lamella transition occurs when aggregates have a crew-cut structure with the thickness of the corona smaller than the radius of the core. Similar to starlike micelles with corona larger than the core, the equil. parameters of crew-cut micelles are detd. by the balance between the free energy of the corona and the surface energy of the core. The elastic free energy of the core remains small compared to the corona and surface free energies; however, it dets. the transitions between different morphologies. The theor. predictions including the existence of crew-cut spherical micelles, the range of stability of cylindrical micelles, and the significance of the contributions of the logarithmic corrections to scaling are in good agreement with expts. on polystyrene-polyisoprene block copolymer micelles in heptane, a selective solvent for the polyisoprene block. on SciFinder(R)]