Order-disorder transition in 2-D sphere forming diblock copolymers

The order disorder transition corresponding to the two dimensional hexagonal patterns formed by sphere forming diblock copolymers is studied through the Cahn-Hilliard model by taking into account a long range term in the free energy functional. The growth kinetic of the equilibrium patterns at deep quenches is dominated by spinodal decomposition. At shallow quenches the phase separation is a two-steps process, initiated by a long lived intermediate state with a well defined characteristic length, but ill defined symmetry. The mean-life of this state increases with a power law with the reduced temperature as the order disorder transition is approached. At long times the system evolutes towards equilibrium by nucleation and growth.