Ordered microphases in binary blends of AB and ABC block polymers

Blending block polymers with different block lengths is a well-established strategy for producing new ordered nanostructures that are difficult to realize in neat block copolymer melts. In this study, we investigate the phase behavior of binary blends of AB diblock copolymer and ABC triblock terpolymer, using self-consistent field theory (SCFT). We present phase diagrams of the blend systems as functions of segregation strength and blend composition, which exhibit a rich phase behavior due to an expansive parameter space with eight independent parameters (three Flory–Huggins interaction parameters, three block compositions, one overall molecular weight ratio, and one blend composition). Changing just one parameter, blend composition, produces complexity in phase behavior with the emergence of unusual core-shell network phases with asymmetric core and shell volume fractions and a new cylinder-in-O⁷⁰ hybrid network phase. Our SCFT calculations suggest that the nonclassical nanostructures are stabilized via interfacial modification induced by preferential localization of blocks of different lengths in the same domain.