Laves Phase Field in a Diblock Copolymer Alloy

Laves phases are a class of tetrahedrally close-packed Frank-Kasper phases with AB2 stoichiometry. While these phases appear as intermetallic line compounds in a variety of metallic alloys, it is challenging to stabilize Laves phases in reconfigurable soft matter because of the substantial difference in preferred volume between the large A particles and small B particles. Surprisingly, perhaps the conceptually simplest approach blending two diblocks with incompatible core blocks has not been explored yet. Using self-consistent field theory, we predict that a Laves phase should emerge as a phase field in the eutectic phase diagram of an AB/B′C diblock copolymer blend if (i) the AB and B′C diblock copolymers are selected such that their neat melts produce bcc phases with the particle volume ratio of the desired Laves phase and (ii) the repulsion between A and C blocks is sufficiently strong to minimize mixing between micelles. This diblock "alloying"approach produces phase behavior that closely mimics that arising in intermetallic compound-producing metal alloys and should provide a relatively simple synthetic route to produce soft Frank-Kasper phases that are challenging to achieve by conventional polymer-based approaches.