Effect of Molecular Asymmetry on the Formation of Asymmetric Nanostructures in ABC-Type Block Copolymers

Abstract

Because domain geometry is dictated by the volume fraction of the block constituting it, an ABC linear triblock copolymer with unequal volume fractions of A and C blocks can form asymmetric ordered morphologies and even hybrid morphologies composed of A and C domains in different geometries. By constructing the triangular phase diagram of ABC triblock with fixed interaction parameters χ AB N = χ BC N = χ AC N using self-consistent field theory, we predict a number of hybrid morphologies, including sphere-lamella, cylinder-lamella, perforated lamella−lamella, and sphere-cylinder. These hybrid morphologies exhibit relatively narrow stable regions as well as simple arrangements of A/C-domains. Furthermore, an interesting class of hybrid morphologies composed of spheres and network is absent, whose absence is mainly caused by the limited regions of spherecontaining hybrid morphologies. Accordingly, we introduce a topological asymmetry by branching BC-blocks at the A/B junction, forming an A(BC) m miktoarm star copolymer. In the phase diagram of A(BC) 2 , we predict three interesting sphere-network hybrid morphologies in considerable regions, including sphere-diamond (SD), spheres within the double-gyroid networks, and sphereperforated lamella. A stable SD over a sphere-gyroid is in striking contrast to stable alternating gyroids over alternating diamonds. When m = 2 is increased to m = 3, another new sphere-network morphology, that is, spheres within the double-diamond networks, is predicted in a considerable region. In addition, we find that the stability regions of these interesting sphere-network hybrid morphologies only shift slightly when χ AB N = χ BC N = χ AC N is changed to χ AB N = χ BC N ≪ χ AC N. In brief, our work demonstrates that the combination of compositional asymmetry and topological asymmetry provides an opportunity for the fabrication of novel hybrid morphologies.

Frank–Kasper Phases in Block Polymers

“…While the SIS′O tetrablock terpolymer has been the focus of experimental studies of Frank–Kasper phase formation in multiblock polymers, ,, other promising multiblock architectures have been proposed and studied by SCFT. − A particularly intriguing candidate is the B 1 AB 2 CB 3 pentablock terpolymer, where the subscripts indicate the B-blocks are all of different degrees of polymerization. This system has been analyzed by SCFT for the case where the Flory–Huggins parameters between chemically dissimilar blocks are equal and large (χ N = 80) .…”

“…Blending and multiblock polymers have proven already to be powerful platforms for expanding the palette of Frank–Kasper phases, for both theoretical predictions ,,− ,− and experimental realization. ,,− ,, The compositional and architectural complexity of multiblock polymers grows rapidly with the number of blocks and number of monomer chemistries, which has been termed a possible Pandora’s box because it makes systematic exploration of the phase diagrams infeasible experimentally and, most often, computationally as well. Even the case of an ABC triblock terpolymer involves three χ ij parameters, two conformational asymmetry parameters, and two volume fractions, and this system is known to produce a large array of different morphologies. , A similar level of combinatorial complexity is introduced by blending along with the additional challenge of macroscopic phase separation in the multicomponent mixture.…”

Hydrogen bonding mediated self‐assembled structures from block copolymer mixtures to mesoporous materials

“…ABC triblock copolymers are also attractive since they can form self‐assembled hierarchical structures different from those of diblock copolymers 73–80 . Nevertheless, using A‐ b ‐B/C‐ b ‐D blends and varying the hydrogen bonding strength is a relatively facile approach toward the preparation of such hierarchical structures while avoiding the generally complicated and difficult synthesis of ABC triblock copolymer 81 .…”

Ultrafast Self-Assembly of Bottlebrush Statistical Copolymers: Well-Ordered Nanostructures from One-Pot Polymerizations

“…Over the past several decades, block copolymers have garnered significant interest in academia and industry due to their ability to microphase separate into well-defined nanoscale structures. − Directed self-assembly, in particular, has been widely explored as an alternative patterning approach for electronic devices and data storage. − However, the self-assembly of linear block copolymers (LBCP) is rather constrained when forming well-ordered, defect-free structures, particularly with large lattice spacings, due to the kinetic frustrations in entangled systems of high-molecular-weight polymers. − In the pursuit of alleviating the constraints in LBCPs and expanding upon the achievable range of nanostructures, recent studies have explored the self-assembly of alternate architectures of copolymers, such as multiblock, mitko star, − comb block copolymers, and bottlebrush block copolymers (BBCP). − BBCPs are densely grafted macromolecules with polymeric side chains tethered to a linear backbone in separate block segments . Combining short side chains with high grafting density leads to a reduction in the overall chain entanglements in the system, increasing molecular mobility and overcoming many barriers of assembly present in entangled LBCPs .…”