Interplay of liquid crystalline ordering in double side-chain liquid crystalline diblock copolymer

Liquid-Crystalline Polymers: Molecular Engineering, Hierarchical Structures, and Applications

Liquid-crystalline polymers (LCPs) are a unique class of soft materials that combine liquid crystal and polymer characteristics. This perspective highlights recent advances of LCPs on the aspects of molecular engineering, hierarchical structures, and emerging applications. The strategy of sequence control in polymer synthesis has been introduced to tailor the primary structures of LCPs as well as their phases and orders. By incorporating mesogenic motifs rich in shape, order, and interaction into LCPs, novel bulk and interfacial structures on hierarchical scales are anticipated. The intrinsic features and fascinating properties of LCPs enable them to find potential applications in emerging areas including integrated circuits, lasing, environment, and energy, implying compelling opportunities for LCPs in fundamental science and transformative technologies.

Iridescence in nematics: Photonic liquid crystals of nanoplates in absence of long-range periodicity

Photonic materials with positionally ordered structure can interact strongly with light to produce brilliant structural colors. Here, we found that the nonperiodic nematic liquid crystals of nanoplates can also display structural color with only significant orientational order. Owing to the loose stacking of the nematic nanodiscs, such colloidal dispersion is able to reflect a broad-spectrum wavelength, of which the reflection color can be further enhanced by adding carbon nanoparticles to reduce background scattering. Upon the addition of electrolytes, such vivid colors of nematic dispersion can be fine-tuned via electrostatic forces. Furthermore, we took advantage of the fluidity of the nematic structure to create a variety of colorful arts. It was expected that the concept of implanting nematic features in photonic structure of lyotropic nanoparticles may open opportunities for developing advanced photonic materials for display, sensing, and art applications.

Discovery of hierarchical superstructures in block copolymers by integrating different liquid crystalline interactions

Hierarchically assembled superstructures of block copolymers are discovered by introduction of the competition of anisotropy attributed from liquid crystalline ordering and nano-phase separation. When the two prototypical fields of liquid crystals (LCs), smectics (S) and nematics (N), are adjoined within the framework of diblock copolymers (S-N) in a variety of precisely tuned compositions, a novel class of superlattices with an interdigitated array of smectic layers between the nearest lamellae or cylinders are observed. This generates unconventional nano-phase separated orthorhombic (Lo) and pseudo-hexagonal (Ho) structures, where the stretched N tethers, projected regularly from the S layers, could transfer the local organization and guide the correlated assembly. This type of superstructure is highly frustrated in reversed cylindrical morphology and absent in S-coil diblock copolymers. The collective interplay of the S and N interactions with nano-phase separation induces the formation of the final complex yet equilibrium structures, providing unprecedented opportunities towards exquisite structural diversity.

Gradient and block side-chain liquid crystalline polyethers

Synthesis of gradient liquid crystalline copolymers is reported for the first time, phase structures of which on multiple length scales with composition and temperature are investigated and compared with the corresponding diblock copolymers.

Influence of alkoxy tail length on the phase behaviors of side-chain liquid crystalline polymers without the spacer

The alkoxy tail plays an important role in the phase behavior of the SCLCPs based on biphenyl mesogen without the spacer.

Hierarchical Nanostructures and Self-Assemblies in Smectic-Nematic Liquid Crystalline Diblock Copolymers

Coexistence of smectic and nematic orders in 3D curvaceous bicontineous cubic or hexagonal hierarchical structures is observed in a novel class of nanophase separated, flexible double liquid crystalline (LC) diblock copolymers of different molecular weights (MWs) but similar compositions, obtained via sequential anionic polymerization. The diblock copolymer of higher MW exhibits an exceptional order-order transition (OOT) from lamellae (Lam) to hexagonal-packed cylinder (HPC) upon nematic ordering. In contrast, the polymer with lower MW forms a thermodynamically stable, ordered gyroid structure, interwining with LC defects on nanoscale. Delicate balance of collective LC interactions and geometric frustration dictates this unique behavior, which offers a genuine way to fine-tune 2D and 3D complex structures with sub-10 nm feature sizes.