Over the past decades,significant attention has been paid to the phase separations in block copolymers and their mixtures due to their potential applications such as nanolithography,fabrication of nanoporous membranes for advanced separation media,and photonic crystals.[1-3] However,how to tailor a desired nanostructure is a problem of using block copolymers.There are a large number of experimental and theoretical works to address the problem.Applied exteal fields,[4] such as electric field,[5-9]shear flow,[10-12] and surface fields,[13-15] are promising candidates to achieve that goal.In particular,surface fields are prominent in confined geometries,such as parallel wall confinement,[16-18] nano-cylinder tube confinement,[18-23] and spherical confinement.[18,24,25]For parallel wall confinement,most studies have focused on pure block copolymer systems.Researchers observed that for highly wall-block interactions,one block component segregates to both interfaces,and the frustration due to incommensuration between film thickness and the diblocks bulk period is accommodated by the formation of layers parallel to the walls with a perturbed period.In contrast,reducing the wall-block interactions allows the frustration to be accommodated by perpendicular ordering of the diblock,such that both block components are present at the walls.