Microscopic Origins of the Distinct Mechanical Response of ABA and ABC Block Copolymer Nanostructures

Self Cite

Metrics & MoreArticle Recommendations * sı Supporting Information ABSTRACT: "Recasting" crystals at the nanoscale or mesoscale has attracted abiding interest. However, how to obtain novel mesocrystals beyond inorganic crystals remains an unsolved challenging problem in the context of block copolymers. We propose simple binary ABC/ABC blends, of which the two linear ABC triblock copolymers consist of the same B-and C-blocks but unequal A-blocks, to self-assemble into novel binary mesocrystals. The long and short A-blocks coassemble into large A-spheres, while the equal C-blocks can only form small C-spheres, resulting in the formation of binary mesocrystals with highly asymmetric coordination numbers (CNs). Moreover, we have established an assumption rule to systematically construct a huge library of binary crystal lattices without resorting to the prototypes of inorganic crystals. Based on this library, we have theoretically predicted seven stable binary mesocrystal phases, including two novel mesocrystals (FCC-AC 8 and FCC-AC 10 ) that are not found in the prototypes of inorganic crystals. This work offers an effective and inexpensive strategy for the experimental preparation of novel binary mesocrystals and therefore is hopeful to stimulate relevant experimental studies.

Section: Introductionmentioning

confidence: 99%

Largely Asymmetric Binary Mesocrystals beyond Inorganic Crystals Formed in Linear ABC/ABC Blends

You,

Xu,

Dong

et al. 2024

Self Cite

Understand the Relative Stability of Single-Gyroid to Double-Gyroid in AB-Type Block Copolymer: Chain Packing and Geometric Analysis

Cheng,

Xu,

2024

It has been commonly accepted that the bicontinuous double-gyroid (DG) network structure is the usual stable phase formed in pure AB-type block copolymer melts. Thus, the emergence of the single-network counterpart, i.e., single-gyroid (SG), is mysterious. In previous work, it was proposed that the SG phase was stabilized by the synergistic effect of the local segregation between two unequal end B-blocks and the stretched bridging middle B 2 -block of the linear B 1 AB 2 AB 3 pentablock; however, this was not sufficiently verified. Here, we reexamine the stabilization mechanism of the single-gyroid phase and reveal that the bridging middle B-blocks do not play a key role in stabilizing the SG phase over DG due to their negligibly low bridging fraction. Instead, the middle B 2 -blocks mainly concentrate near the interface in the form of loops, helping the short end B 1 -block to push the long B 3block to fill the further space and thus relieving the packing frustration of B-blocks in the matrix of SG on the one hand. On the other hand, the middle B-block is distributed more uniformly on the interface in the SG structure than in the DG structure due to the more uniform interfacial curvature of the former. These two factors lower the relative interaction energy of SG compared to DG, consequently stabilizing SG. Clearly elucidating the stabilization mechanism of SG may provide guidance for further improving its stability or obtaining other single-network phases (e.g., single-diamond).

Enhancement of Mechanical Performance of Nanostructured Materials by Architectural Design of Pentablock Terpolymers

Zeng,

Lin,

Zhang

2024

Nanostructured materials consisting of multiple ordered domains can achieve a much broader range of enhanced properties in comparison with their constituent counterparts. Nanostructure engineering of block copolymers provides a potent platform for the rational design of nanostructured materials due to their broad structural palette and diverse architectures. In this contribution, integration of dynamic self-consistent field theory and lattice spring model is harnessed to investigate the nanophases and mechanical properties of nanostructured materials of architecture-designed B1AB2CB3 pentablock terpolymers, composed of incompatible A and C blocks as well as distinct B blocks with various lengths. By virtue of the change of the molecular architecture of pentablock terpolymers, a wide spectrum of spherical crystal-like nanostructures is predicted, and their structural evolution in the course of microphase separation obeys a stepwise ordering mechanism. In particular, the local segregation of the distinct B blocks provides an effective and feasible means to spatiotemporally regulate the bridge configuration of inner B2 blocks in the matrix. More importantly, the architectural design of pentablock terpolymers plays a crucial part in enhancing the mechanical performance of nanostructured materials originating from various mechanical nanolattices of truss-based analogues. The obtained results provide fundamental insight into the formation of self-assembled nanostructures of multiblock terpolymers and offer a means for boosting the mechanical properties of nanostructured materials by the architectural design of macromolecules without a change of composition.