Hierarchical Self-Assembly of ABC-Type Bottlebrush Copolymers

We have performed dissipative particle dynamics simulationstostudy the self-assembly of ABC-type bottlebrush copolymers (BBCPs),one portion of whose backbone is grafted by pairs of A-blocks andthe other portion is grafted by B/C-blocks in pairs, focusing on theeffects of the number of A side chains, the length of B side chainsrelative to that of C side chains, and the rigidity of the backboneon the formation of hierarchical structures. A number of hierarchicalstructures with the superstructures formed by the phase separationbetween A and B/C-blocks and the substructures formed by the phaseseparation between B and C-blocks are observed. Some hierarchicalstructures are similar to those self-assembled by ABC star copolymers,whereas their stable parameter regions of ABC-type BBCPs are muchlarger. On the other hand, the ABC-type BBCPs can also form some novelhierarchical structures that are hard to form in ABC star copolymers.Though the formation of the A-superstructure and the B-substructurein many hierarchical structures can be independently controlled, thereare also some hierarchical structures in which the transitions ofthe superstructure and substructures are coupled. In other words,the A-superstructure changes along with the transformation of theB-substructure for fixed f (A). In addition,our results demonstrate that the rigidity of the backbone has a significanteffect on the formation of the hierarchical structure in ABC-typeBBCPs, i.e., a rigid backbone favors the normal arrangement of B-substructuresto A-superstructures. Our work not only deepens the understandingof the self-assembly mechanism of ABC-type BBCPs but also provideshelpful guidance for experiments to fabricate interesting hierarchicalstructures.