5 nm Ordered Structures Self-Assembled by C2 -Symmetric Hybrids with Polyhedral Oligomeric Silsesquioxane and Hexa-peri-Hexabenzocoronene.

Hybrids consisting of polyhedral oligomeric silsesquioxane (POSS) and hexa-peri-hexabenzocoronene (HBC) with a dumbbell topology and C2 symmetry were designed and synthesized. They self-assemble into 5 nm ordered structures. In particular, the increased steric effect with increasing POSS units stabilizes a square columnar phase (Colsqu ) which is important in nanotemplating. These hybrids containing discotic liquid crystal HBC and POSS units have an excellent etching contrast and present an approach to obtain 5 nm nanopatterns.

Hierarchically ordered structures of disk-cube triads containing hexa-peri-hexabenzocoronene and polyhedral oligomeric silsesquioxane.

Obtaining nanoscale-ordered structures is important for the development of nanotechnology. We designed and synthesized a series of disk-cube triads containing one hexa-peri-hexabenzocoronene (HBC) and two polyhedral oligomeric silsesquioxane (POSS) moieties, HBC-2POSS. The two POSS units were linked via ester or amide bonds. With the amide linkage used, the hydrogen bonding that was introduced affected the balance between the π-π interaction of HBC cores and crystallization interaction of POSS units. Hierarchically ordered structures were obtained from HBC-2POSS triads owing to the synergistic effect of multiple secondary interactions: π-π interaction, hydrogen bonding, and crystallization interaction. As organic-inorganic hybrid materials, these HBC-2POSS triads are promising candidates for templates <10 nm.

Head-Tail Asymmetry as the Determining Factor in the Formation of Polymer Cubosomes or Hexasomes in a Rod-Coil Amphiphilic Block Copolymer.

The self-assembly of a rod-coil amphiphilic block copolymer (ABCP) led to Im3‾ m and Pn3‾ m polymer cubosomes and p6mm polymer hexasomes. This is the first time that these structures are observed in a rod-coil system. By varying the hydrophobic chain length, the initial concentration of the polymer solution, or the solubility parameter of the mixed solvent, head-tail asymmetry is adjusted to control the formation of polymer cubosomes or hexasomes. The formation mechanism of the polymer cubosomes was also studied. This research opens up a new way for further study of the bicontinuous and inverse phases in different ABCP systems.

Patterning of Discotic Liquid Crystals with Tunable Molecular Orientation for Electronic Applications.

The large-area formation of functional micropatterns with liquid crystals is of great significance for diversified applications in interdisciplinary fields. Meanwhile, the control of molecular alignment in the patterns is fundamental and prerequisite for the adequate exploitation of their photoelectric properties. However, it would be extremely complicated and challenging for discotic liquid crystals (DLCs) to achieve the goal, because they are insensitive to external fields and surface chemistry. Herein, a simple method of patterning and aligning DLCs on flat substrates is disclosed through precise control of the formation and dewetting of the capillary liquid bridges, within which the DLC molecules are confined. Large-area uniform alignment occurs spontaneously due to directional shearing force when the solvent is slowly evaporated and programmable patterns could be directly generated on desired substrates. Moreover, the in-plane column direction of DLCs is tunable by slightly tailoring their chemical structures which changes their self-assembly behaviors in liquid bridges. The patterned DLCs show molecular orientation-dependent charge transport properties and are promising for templating self-assembly of other materials. The study provides a facile method for manipulation of the macroscopic patterns and microscopic molecular orientation which opens up new opportunities for electronic applications of DLCs.

Shape effect-induced spiral superstructures in a self-assembled achiral disc-bent core amphiphile.

Herein, we aim to demonstrate the shape effect of a giant molecule on the self-assembly of supramolecules. A bent-core (BC) molecule was covalently linked to a disc-like hexa-peri-hexabenzocoronene (HBC), giving a disc-bent core amphiphile. As a result, the induced hierarchical chirality driven by the shape effect on the forming columnar phase gives a two-dimensional nano-ribbon with spiral texture from double-stranded supracolumns.

Hierarchical Self-Assembly of Disc-Rod Shape Amphiphiles Having Hexa-peri-hexabenzocoronene and a Relatively Long Rod.

Two disc-rod shape amphiphiles consisting of hexa-peri-hexabenzocoronene (HBC) and a nanosized rodlike mesogen were designed and synthesized. Thermotropic phase behaviors were carefully studied. Despite significant steric mismatch between the discs and rods, hierarchical structures were observed for both disc-rod shape amphiphiles at ambient temperature and upon heating. Molecular packing schemes were proposed and confirmed using the reconstructed electron density maps, molecular dynamics simulation, and direct observation using transmission electron microscope. The results demonstrate that the shape effect is of great importance in the self-assembly of shape amphiphiles.

Exploiting Host-Guest Interactions for the Synthesis of a Rod-Rod Block Copolymer with Crystalline and Liquid-Crystalline Blocks.

By making use of the host-guest interactions between the host molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and the rod-coil block copolymer (BCP) poly(ethylene oxide)-block-poly(octyl 4'-octyloxy-2-vinylbiphenyl-4-carboxylate) (PEO-b-PVBP), the supramolecular rod-rod block copolymer P(EO@TPP)-b-PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid-crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed. The self-assembled nanostructure is thus clearly affected by the interplay between the two blocks. On the basis of wide- and small-angle X-ray scattering analysis, we conclude that the supramolecular rod-rod BCP can self-assemble into a cylinder-in-cylinder double hexagonal structure.

The synthesis and self-assembly of disc-cube dyads with spacers of different lengths.

Disc-cube dyads with a polyhedral oligomeric silsesquioxane (POSS) molecule covalently attached to a hexa-peri-hexabenzocoronene (HBC) molecule were designed and synthesized. The results demonstrate that the length of a spacer plays an important role in the self-assembly behavior of the HBC-POSS dyad.