Asymmetric Diblock Copolymer Thin Film Confined in a Slit: Microphase Separation and Morphology

Abstract

Microphase separation and morphology of asymmetric diblock copolymer (f = 0.4) thin films confined in a slit with surfaces neutral or attractive towards block A or block B were studied by the cell dynamic system method (CDS). The size effect in CDS calculations was carefully investigated. For asymmetric copolymers, the size effect is important even in the case of attractive walls. Not only must we use boxes with larger sizes in the X- and Y-directions, the size is also dependent on the film thickness. In contrast, for symmetric copolymers, the size effect is not serious when we adopt attractive plates. Various microdomain morphologies including regular lamellae adjacent to the surfaces, mesh-like layers with nanosized spheres dispersed in a matrix of block A, and flexuous cylindrical phases are found in this work. A series of conditions we can control, such as the chemical composition of the copolymer, the thickness of the film, the selective interactions between plates and blocks as well as their strength, all make the potential technology more adaptable. To test the reliability of the CDS method, the results are compared with those from dynamical density functional theory and Monte Carlo simulation.