Examination of well ordered nanonetwork materials by real- and reciprocal-space imaging

Encounter between Gyroid and Lamellae in Janus Colloidal Particles Self-Assembled by a Rod-Coil Block Copolymer

Controlling the internal structure of block copolymer (BCP) particles has a significant influence on its functionalities. Here, a structure-controlling method is proposed to regulate the internal structure of BCP Janus colloidal particles using different surfactants. Different microphase separation processes take place in two connected halves of the Janus particles. An order-order transition between gyroid and lamellar phases is observed in polymeric colloids. The epitaxial growth during the structural transformation from gyroid to lamellar phase undergoes a two-layered rearrangement to accommodate the interdomain spacing mismatch between these two phases. This self-assembly behavior can be ascribed to the preferential wetting of BCP chains at the interface, which can change the chain conformation of different blocks. The Janus colloidal particles can further experience a reversible phase transition by restructuring the polymer particles under solvent vapor. It is anticipated that the new phase behavior found in Janus particles can not only enrich the self-assembly study of BCPs but also provide opportunities for various applications based on Janus particles with ordered structures.

Electron Crystallographic Investigation of Crystals on the Mesostructural Scale

The precise structural solution of crystals on a mesostructural scale is challenging due to the difficulties in obtaining electron diffraction and the complicated relationship between the crystal structure factors (CSFs) and the conventional underfocus phase-contrast transmission electron microscopy (TEM) images due to the large unit cell and the complex structures. Here, we present the structural investigation of mesostructured crystals via the combination of electron crystallographic Fourier synthesis and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that only relies on the mass-thickness contrast. The three-dimensional electrostatic potential is reconstructed from the amplitudes and phases extracted from the Fourier transforms of the corresponding HAADF-STEM images and merged into a set of CSFs. This method is verified on silica scaffolds following a shifted double-diamond surface network with space group I41/amd. The results indicate that electron crystallography reconstruction by HAADF-STEM images is more suitable and accurate in determining the structure in comparison with conventional TEM electron crystallography reconstruction. This approach transfers the contrast of mesostructured crystals to images more accurately and the relationship between the Fourier transforms of HAADF-STEM images and the CSFs is more intuitive. It shows great advantages for the structural solution of crystals on the mesostructural scale.

Mesochiral phases from the self-assembly of chiral block copolymers

Self-assembly of block copolymers with chiral sense gives mesochiral phases possessing helical sense. With the controlled chirality of the helical cylinder and chiral network, it is appealing to fabricate chiral materials for applications.

Computational and materials structural science

This Editorial discusses recent development in computational and materials structural science as exemplified by recent articles published in IUCrJ.