The effect of the median selective solution on the lamellar,spherical and gyroid structures is studied. The self-consistent field equations of the diblock copolymer solution are solved by using the reciprocal space method. It is shown that the spherical and gyroid phases have the lowest free energy in the certain range of the solution concentration. Furthermore,the phase diagram of the ordered structures in the diblock copolymer solution with the median selective solvent is calculated,which is consistent with the experimental results.
