Phase behavior and interfacial properties of diblock copolymer-homopolymer ternary mixtures: Influence of volume fraction of copolymers and interaction energy

Abstract

We use a Monte Carlo method to study the phase and interfacial behaviors of A-b-B diblocks in a blend of homopolymers, A and B, which are confined between two asymmetric hard and impenetrable walls. Our results show that, when the interaction strength is weak, the block copolymers are uniformly distributed in the ternary mixtures under considered concentrations. Under strong interaction strength, distribution region of the block copolymers changes from a single smooth interface to a curved interface or multi-layer interface in the ternary mixtures. Furthermore, our findings show that with increasing volume fraction of A-b-B diblock copolymer (ϕ C), copolymer profiles broaden while ϕ C ≥ 0.4, a lamellar phase is formed and by further increasing ϕC, more thinner layers are observed. Moreover, the results show that, with the increase of ϕ C, the phase interface first gradually transforms from plane to a curved surface rather than micelle or lamellar phase while with the increase of the interaction between A and B segments (e AB), the copolymer chains not only get stretched in the direction perpendicular to the interface, but also are oriented. The simulations also reveal that the difference between symmetric and asymmetric copolymers is negligible in statistics if the lengths of two blocks are comparable.