Surface-induced morphologies of lamella-forming diblock copolymers confined in nanorod arrays

Using the real-space self-consistent field theory, we investigate the effects of geometry confinement and surface field on the morphologies of lamella-forming diblock copolymers confined in the periodic nanorod arrays. The array confinement provides a fractional confinement dimension where the diblock copolymers are incompletely confined at each spatial direction and the novel morphologies may be surface induced. In the arrays with neutral surfaces, we observe several confinement-induced morphologies, such as perpendicular lamellae and double-cylinder network structures, by varying the degree of confinement. For the arrays with preferential surfaces, a rich variety of morphologies including undulated lamellae, perforated lamellae, and cylindrical lamellae are investigated as a function of the strength of surface field. The predicted morphologies and the corresponding ordered transitions can be reasonably comprehended based on the commensurability between the array period and the bulk lamella period, as well as the cylindrical symmetry about the surface field.