Morphology and Phase Diagram of Complex Block Copolymers: ABC Star Triblock Copolymers

Abstract

Microphases and triangle phase diagrams of ABC star triblock copolymers are investigated on the basis of a real-space implementation of the self-consistent field theory (SCFT) for polymers. For the sake of numerical tractability, the calculations are carried out in two dimensions (2D). Nine stable microphases are uncovered, including hexagonal lattice, core-shell hexagonal lattice, lamellae, and lamellae with beads at the interface as well as a variety of complex morphologies that are absent in linear ABC triblocks, such as a three-color hexagonal honeycomb phase, knitting pattern, octagon-octagon-tetragon phase, lamellar phase with alternating beads, and decagon-hexagon-tetragon phase. We have found that when the volume fractions of the three species are comparable the star architecture of the polymer chain is a strong topological constraint that regulates the geometry of the microphases formed. However, when at least one of the volume fractions of the three species is low, the influence of the star architecture on the morphology is not significant. Our calculations reasonably agree with previous theoretical and experimental results and can be used to guide the design of novel microstructures involving star triblock copolymers.