Laves Phases Emerge in Neat AB-Type Block Copolymer as Hybrid Spherical Phases

Soft spherical domains assembled from block copolymers can pack into Frank-Kasper phases, reminiscent of those found in alloys. As a special subcategory of Frank-Kasper phases, Laves phases are particularly challenging to obtain. So far, the most stable Laves phases have been realized in copolymer blends, where mixing different polymers accommodates the size discrepancy between the two types of spheres. Here, we propose an intramolecular blending strategy to stabilize Laves phases in neat AB-type block copolymer melts. By designing multiblock copolymers with two separate A blocks in different topological environments, we predict stable Laves phases within a substantial parameter window using self-consistent field theory, together with several hybrid phases. We find that Laves phases can be regarded as a hybrid structure to some extent, so they resemble the stabilization mechanism as the usual hybrid structures; that is, the two A-blocks can adapt to two different interface curvatures. Our intramolecular blending strategy provides an effective way for stabilizing novel ordered structures, especially those hybrid structures with bimodal interfacial curvatures, by rationally designing the architecture of block copolymer.