Asymmetric Organic–Inorganic Hybrid Giant Molecule: Cyanobiphenyl Monosubstituted Polyhedral Oligomeric Silsesquioxane Nanoparticles for Vertical Alignment of Liquid Crystals

Abstract

For liquid crystal (LC) alignment, polyhedral oligomeric silsesquioxanes (POSS) can be considered as one of the promising candidates for the formation of vertical alignment (VA) of LC. However, because of their poor compatibility and weak interaction with LC hosts, the pristine POSS are highly aggregate themselves in the LC media and create the macroscopic particles, resulting in severe light scatterings. To overcome this barrier, we proposed and successfully synthesized the cyanobiphenyl monosubstituted POSS giant molecule (abbreviated as POSS-CBP 1 ), which showed an excellent dispersion in nematic (N) LC media and formed the perfect VA of LC without using conventional polymer-based VA layers. On the basis of the systematic experiments and careful analysis, we realized that the cyanobiphenyl moiety chemically attached to the pristine POSS with an alkyl chain can significantly improve the initial solubility and interaction with LC media but finely tune POSS-CBP 1 to gradually diffuse onto the substrate of LC cell for the formation of VA layer without forming the macroscopic aggregations. Therefore, the newly developed POSS-CBP 1 VA layer can allow us to significantly cut the manufacturing cost as well as to open the new doors for electro-optical applications.

Directed Self‐Assembly of Liquid‐Crystalline Molecular Building Blocks for Sub‐5 nm Nanopatterning

“…Copyright 2011, Royal Society of Chemistry. e) Reproduced with permission . Copyright 2014, American Chemical Society.…”

Polyhedral Oligomeric Silsesquioxane Films for Liquid Crystal Alignment

“…Colloids Interfaces 2018, 2, x FOR PEER REVIEW 2 of 8 giant molecules [13]; but the proposed method in this work presents an alternative. A), transcyclohexanediolisobutyl-POSS (POSS B), and 1,2-propanediolisobutyl-POSS (POSS C), were all purchased from Sigma-Aldrich (St. Louis, MO, USA) and used in the experiment without further treatment and purification.…”

“…As shown in Figure 1, each POSS contains reactive functional groups for polymerization and nonreactive functional groups for solubility in the different polymer systems [9]. POSS nanomaterials have been widely incorporated into different molecules to change those molecules' physical and chemical properties in efforts to produce different functional materials [10][11][12][13][14][15][16].…”

“…However, the dispersion of POSS nanomaterials in the LC layer is not easy to control, and POSS aggregation is easily formed in the LC layer; therefore, some scattering is produced around the POSS aggregation, which reduces the contrast of LCDs. The aggregation issue may be overcome by complicated chemical synthesis, such as using cyanobiphenyl monosubstituted POSS giant molecules [13]; but the proposed method in this work presents an alternative. The influences of the POSS functional group and the morphology of the POSS alignment film on the properties of LC alignment were investigated.…”

Multifunctional Optical Thin Films Fabricated by the Photopolymerization of Uniaxially Oriented Lyotropic Liquid Crystal Monomers for Electro-Optical Devices

“…In addition, high-molecular weight polymers possess high viscosity which leads to long annealing times at high temperatures with toxic solvents17. To overcome the drawbacks of traditional alignment layers, many alternative methods including photo-alignment layers and self-assembled alignment layers have been introduced1819202122. In parallel to the development of alignment layer, the coatable multifunctional optical thin films wherein the single film functions both as the alignment layer and polarizer have been intensively required from optoelectronic device engineers for the fabrication of flexible displays and devices2324252627.…”