Binary Blends of Diblock Copolymers: An Efficient Route to Complex Spherical Packing Phases

Abstract The phase behavior of binary blends composed of AB and AB diblock copolymers is systematically studied using the polymeric self‐consistent field theory, focusing on the formation and relative stability of various spherical packing phases. The results are summarized in a set of phase diagrams covering a large phase space of the system. Besides the commonly observed body‐centered‐cubic phase, complex spherical packing phases including the Frank–Kasper A15, and the Laves C14, C15 phases could be stabilized by the addition of longer AB‐copolymers to asymmetric AB‐copolymers. Stabilizing the complex spherical packing phases requires that the added AB‐copolymers have a longer A‐block and an overall chain length at least comparable to the host copolymer chains. A detailed analysis of the block distributions reveals the existence of inter‐ and intra‐domain segregation of different copolymers, which depends sensitively on the copolymer length ratio and composition. The predicted phase behaviours of the AB/AB diblock copolymer blends are in good agreement with previous experimental and theoretical results. The study demonstrates that binary blends of diblock copolymers provide an efficient route to regulate the emergence and stability of complex spherical packing phases.