Blends of Two Diblock Copolymers with Opposite Phase Behaviors

The phase behavior of blends of A-b-B and A-b-C diblock copolymers with opposite self-assembly tendencies are studied, where the former exhibits the assembly upon heating and the latter shows the assembly upon cooling. A compressible random-phase approximation (RPA) theory and a Ginzburg-Landau simulation based on the RPA are first extended to such copolymer blends. It is shown that a delicate balance in self and cross interactions between constituent monomers can yield various phase behaviors covering the assembly upon heating, loop-type assembly, and assembly upon cooling by varying the blend composition. In particular, the loop-forming blend reveals the tremendously enhanced pressure sensitivity of the ordering temperatures, which can prove useful in pressure-related nanofabrication.