Although the double-gyroid (DG) structure has been commonly formed from the self-assembly of block copolymers, the singlegyroid (SG) structure is rarely reported. Moreover, the SG structure even shows better performance than DG in some optical applications. How to prepare the SG structure has become an attractive but challenging topic. We speculate that the SG structure can be stabilized by the synergistic effect of released packing frustration and stretched bridging block in AB-type block copolymers. Accordingly, we propose the minimum conditions for the design of architecture that enables the two mechanisms simultaneously. Following these conditions, a simple linear BABAB pentablock copolymer is successfully devised. SCFT calculations confirm that the SG phase can be stabilized by tailoring the architecture. Our work is hopeful to promote relevant experimental studies for engineering the unusual SG structure.

Both experimental and theoretical studies have shown that a cylinder-forming block copolymer melt under the confinement of a nanopore can self-assemble into an interesting sequence of ordered nanostructures in terms of the pore size, including single cylinder, stacked disks, single helix, double-helix, and so on. However, most of these studies focused on the normal cylinder phase formed by a simple AB diblock copolymer at a low volume fraction (e.g., f A of A-block). Whether this phase sequence is universal or specifically depends on the copolymer architecture is a question to be answered. In particular, when an “inverted” A-cylinder phase is formed by a special type of AB block copolymer at a high volume fraction of f A > 0.5, for example, the A­(AB) n miktoarm star copolymer, whether the phase sequence still exists is an interesting question. In this work, we investigate the self-assembly of cylinder-forming A­(AB) n copolymer confined in nanopores using the pseudospectral method of self-consistent field theory coupled with the masking technique. By varying the arm number n and the ratio τ of the linear A-block to the total A-blocks, the volume fraction of the bulk A-cylinder phase region of A­(AB) n changes in a large range even for a fixed χN = 60, allowing us to study the cases of a normal cylinder and an inverted cylinder. Our results reveal that the common phase sequence can only be maintained when the cylinder phase is not close to the boundaries of its phase region, as in the case of the pore wall attracting the B-blocks; otherwise, some structures will disappear. For example, the double-helix structure disappears when the cylinder phase is close to the cylinder/gyroid boundary. In contrast, the phase sequence becomes more robust in the case of the pore wall attracting the A-blocks. In both cases of surface preference, stable helical structures are predicted for an inverted cylinder with the volume fraction as large as f A = 0.64. For f A ≥ 0.5, the packing frustration of short B-blocks is severe, leading to a lot of astonishing distortions to many structures. Our work not only deepens the understanding on the self-assembly of block copolymers under cylindrical confinement but also provides guidance for the experimental preparation of helical structures with large volume fractions.

Flow-driven translocation of micelles self-assembled from amphiphilic diblock copolymers through a nanochannel is studied by using hybrid lattice-Boltzmann molecular dynamics simulations. It is discovered that the structure of the translocating micelles depends on their initial sizes. Intact translocation occurs for small micelles, whereas fragmented translocation takes place for large micelles. The fragmented micelles reassemble to form an intact micelle after translocation. Coexistence of these two translocation modes is observed when the size of the initial micelle core is similar to that of the nanochannel. The critical translocation flow flux, at which the probability of translocation equals to 0.5, is found to increase rapidly with the aggregation number of the initial micelles in the intact translocation regime, whereas it remains approximately a constant in the fragmented translocation regime. The number of fragmented translocating micelles is found to be a linear function of the aggregation number. These findings provide an understanding of the dynamics of micelle translocation.

We have investigated the self-assembly of the AB2C terpolymer using self-consistent field theory, focusing on the formation of novel “connected” binary spherical phases. Our results reveal that the AB2C four-arm star terpolymer exhibits significantly different phase behaviors from those of the conventional ABC star terpolymer. Specifically, some polygon-tiling patterns, which are the usual stable phases of the ABC star, do not appear in the phase diagram of the AB2C four-arm star, while the ZnS and NaCl binary spherical phases exhibit large stable regions instead. The volume fractions of the binary spherical domains reach so high that they are severely deformed from being spherical. Interestingly, the binary spheres in ZnS and NaCl structures are in close contact due to the star architecture and thus constitute single diamond and single plumber’s nightmare networks, respectively. Our further calculations indicate that the ZnS structure with a largely tunable volume fraction can be used to generate the template of three-dimensional photonic crystals that have large-sized band gaps. Our work not only deepens the understanding of ABC multi-arm star copolymers but may also promote relevant experimental studies.

Blending two different AB diblock copolymers provides a simple way to enlarge the volume fraction of spherical domains and thus to stabilize various Frank−Kasper spherical phases. What are the limits of the volume fraction and the difference between the two AB diblock copolymers that can be accommodated into a spherical phase? To answer this question, we extend the phase diagram of the binary AB/AB blends by pushing the bidispersity to high degrees based on the calculation of the self-consistent field theory, focusing on the formation of the spherical phases. We find that the average volume fraction of A-blocks for Frank−Kasper A-spherical phases reaches 0.4, which is even larger than the limit obtained by the miktoarm AB n copolymer as n approaches infinity. More surprisingly, a novel "binary" HCP-type spherical structure (HCP b ) is discovered when the two AB diblocks differ greatly in both volume fraction and polymerization degree. The HCP b phase contains large spheres of the core−shell structure co-assembled by two AB diblocks and small spheres formed by nearly pure short AB diblocks. Our work not only deepens the understanding of the self-assembly of AB/AB blends but also may promote relevant experimental studies.