Tunable helical structures formed by blending ABC triblock copolymers and C homopolymers in nanopores

Abstract

AbstractABC triblock copolymers with frustrated interactions of χACN ≪ χABN ~ χBCN confined in nanopores with A‐block‐attracting surfaces can self‐assemble into helical morphologies, where the B blocks form helical domains wrapping around C‐core cylinders within the A shell. It has been suggested that the number of helical strands (m) increases as the volume fraction of C block (fC) decreases, while the increasing m is restricted because C blocks forming domains cannot maintain a cylindrical shape as fC gradually decreases, and the B block domains transform from helical structures to toroidal domains. To prevent the restriction of increasing m, in the current study we added C homopolymers into nanopores. For a given triblock copolymer with (χABN, χBCN, χACN) = (80, 80, 20) and (fA, fB, fC) = (0.7, 0.1, 0.2), varying the concentration (ϕH) and the chain length (γ) of the C homopolymers, as well as the diameter (D) of the nanopores, we constructed different two‐dimensional phase diagrams with respect to two of these control parameters using self‐consistent field theory. A number of helical structures with strands ranging from 1 to 6 are predicted. Our calculations indicate that m increases with increasing γ and D and decreasing ϕH. The theoretical results demonstrate that blending of homopolymer with one given triblock terpolymer could provide an efficient route to fabricate different complex helical nanostructures. © 2021 Society of Industrial Chemistry.