Effect of Conformational Asymmetry on the Stability of Network Phases in Diblock Copolymer Melts

Despite the great success in understanding the microphase separation and the self-assemblies of periodic microstructures in block copolymer systems, stabilization of exotic ordered co-continuous network structures beyond double-gyroid remains a challenge. Motivated by the ability of conformational asymmetry to stabilize Frank-Kasper phases in sphere forming morphologies, we perform simulations using self-consistent field theory (SCFT) to investigate the influence of conformational asymmetry on the stability of network phases in a diblock copolymer melt. The free energies of nine network structures, as well as competing non-network structures, are analyzed. The free energy comparison indicates O⁷⁰, which is stable for conformationally symmetric systems, continues to be an equilibrium morphology in a narrow composition window for high conformational asymmetry, while O⁵² is slightly less stable than O⁷⁰ throughout the whole phase diagram. More exotic network phases remain metastable in the presence of conformational asymmetry. Nevertheless, conformational asymmetry has a significant influence on the relative stability of the network phases, which may provide insights into how a complex network might be stabilized in more complex systems.