Phase Behavior of Frustrated ABC2 Miktoarm Star Triblock Copolymer

The phase behavior of ABC triblock copolymer can be classified into “nonfrustrated” and “frustrated” cases according to the relative strength of the three Flory-Huggins interaction parameters. In the frustrated case, χ_ACN is much weaker than χ_ABN and χ_BCN. Thus, the triblock copolymers prefer to form structures with A/C interfaces. Under the competition of interfacial energy and the entropic energy, the phase behavior of ABC triblock copolymer is more complex, and it can form the phases of the Knitting pattern, double and triple helices on cylinders. However, stable single helical structure has not been reported yet. In order to get the stable single helical structure, we designed the molecule structure of ABC₂ miktoarm star triblock copolymer. Our design principle sheds light on the phase behavior of the frustrated case as well as the spontaneous curvature induced by the conformational asymmetry. Through the calculation of Self-Consistent Field Theory (SCFT), the triangular phase diagram shows the region of stable single helical structure as well as the knitting pattern phases.