Peculiar Phase Morphologies from Twisting of Self-Assembled Ribbons in Chiral Block Copolymers

The chirality effects on BCP self-assembly gives rise to the formation of helical phase (H*) from the self-assembly of polylactide-based chiral block copolymers (BCPs*) with achiral segment-rich fraction. The formation of the helical cylinder is attributed to the packing of helical chains with which twisted cylinder microdomain can be formed from twisting and shifting. By contrast, twisted ribbon with a bilayer-like lamellar texture can be formed in self-assembled polylactide-based BCPs* with chiral segment-rich fraction from twisting and bending. Those twisted ribbons can be further developed to give peculiar phase morphologies in bulk through scrolling, giving a roll cake and concentric lamellar textures. We speculate that those helical and twisted textures are built from the chiral interface of chiral and achiral segments as proposed by the tilted chiral lipid bilayer (TCLB) theory and also the mesochiral assembly of the helical chains predicted by the orientational self-consistent field theory (oSCFT). With the homochiral evolution from helical conformation to hierarchical superstructure via inter-chain chiral interactions, it is appealing to control the handedness of the forming morphologies from BCPs*.