Surface-induced phase transitions in dense nanoparticle arrays of lamella-forming diblock copolymers

The surface-induced phase transitions in dense nanoparticle arrays of lamella-forming diblock copolymers are investigated by using the real-space self-consistent field theory. The dense nanoparticle array provides a distinct and strong confinement environment where there are incomplete confinements in three spatial directions. Several complicated phases with cubic symmetries, such as the monocontinuous and bicontinuous phases, are identified in the dense nanoparticle arrays. Through adjusting the strength of surface preference, the disorder phases are induced into the complicated order phases in the nanoparticle arrays with small periods while the order-order transitions occurs in those with large periods. Investigations on the free and entropic energies indicate that these surface-induced phase transitions are of first-order and the stabilities of order phases are intimately correlated to the strength of surface preference. Our results enrich the knowledge about the phase behaviors of macromolecules in confined systems, which may be helpful to fabricate the novel nanomaterials based on the block copolymers.