Self-assembly of (A-comb-C)-b-(B-comb-C) diblock copolymer-based comb copolymers

The phase behavior of (A-comb-C)-b-(B-comb-C) diblock copolymer melts is investigated using the strong segregation theory approach. Three different regimes are distinguished. In regime 1 both disordered comb blocks are microphase separated from each other, in regime 2 the side chains C are microphase separated from the disordered A-b-B diblock backbones, and, finally, in regime 3 all species A, B, and C are microphase separated. In the first regime the behavior is similar to that of a simple diblock copolymer melt with a renormalized Flory-Huggins interaction parameter. In regime 2 the region of stability of the different phases is significantly changed compared to simple diblocks due to the comb architecture. The fully microphase separated case, regime 3, is characterized by hierarchical structure formation. We restrict the analysis to systems where self-assembly results in the formation of alternating C layers and internally microphase separated AB layers. The latter consist of alternating A and B layers or disks of the minority component. In the former case, the A and B layers are generally perpendicular to the C layers. The parallel orientation is only possible for small grafting densities.