The phase behavior of linear ABCBA pentablock terpolymers is examined and compared with corresponding linear ABC triblock terpolymers by using the 3-D selfconsistent field theory. In particular, phase diagrams of the melts are constructed and used to discuss how the selfassembled morphologies are influenced by the compositions of the three components and the block number per chain. Since the two free ends of A blocks in the ABCBA copolymers enable the macromolecules to relieve the packing frustration within the structures as well as more types of chain conformation, the ABCBA pentablocks exhibit diverse complex network structures and binary crystalline phases of cylinders and spheres. Compared with most linear diblock and triblock copolymers, for which the gyroid phase occupies a narrow region in the phase space, the ABCBA pentablocks tend to form a variety of continuous networks including diamond, hexagonally perforated lamellae, Fddd network, and gyroid. Moreover, the ABCBA pentablocks exhibit different packing orders of alternating A/C spheres and cylinders than ABC. By varying the length of the B-blocks and the ratio of compositions of A and C, a large number of binary metallic and ionic crystals, such as NaCl, CsCl, ZnS, CaF 2 , Li 3 Bi, Nb 3 Sn (A15), and Cu 3 Au, and alternating A/ C cylinders with coordination numbers of A/C equal to 4/4, 6/3, and 4/2, are obtained from the ABCBA pentablock terpolymers. As our simulated ABCBA pentablock terpolymers have synthetic advantages, the fascinating self-assembling results displayed in this study enable the ABCBA as being one of the most efficient routes to functional materials.

No abstract

No abstract

The effects of compositions, interaction parameters, and number of blocks on the self‐assembly of nonfrustrated ABCBA linear pentablock terpolymer melts are investigated and compared with the corresponding ABC linear triblock terpolymers using the self‐consistent field theory. For the case of symmetric interaction parameters (χABN = χBCN) and majority B‐blocks, both ABC triblocks and ABCBA pentablocks can form intriguing A‐ and C‐domains embedded in the B‐matrix. While these morphologies persist in the ABC systems when the segregation strength is decreased, the A blocks tend to mix with the B blocks in the ABCBA pentablocks due to the chain topology, resulting in the formation of C‐domains embedded in the AB‐mixed matrix. Different phase behavior is observed for the case of asymmetric interaction parameters (χABN < χBCN). Aside from the core–shell type structures, a number of morphologies arise due to the separation between C and AB‐mixed domains in ABCBA pentablock copolymers. The theoretical results not only capture the self‐assembling behavior of poly(isoprene‐b‐styrene‐b‐ethylene oxide‐b‐styrene‐b‐isoprene) pentablocks, but also provide concrete suggestions for designing diverse microstructures in the linear ABC‐type terpolymers.

No abstract