Design and Synthesis of Chiral Nematic Liquid Crystals

Abstract

The article contains sections titled: Introduction to the Chiral Nematic Phase and Its Properties Formulation and Application of Chiral Nematic Liquid Crystal Mixtures Applications of Chiral Nematic Phases Classification of Chiral Nematic Liquid‐Crystalline Compounds Aspects of Molecular Symmetry for Chiral Nematic Phases Type I Chiral Nematic Liquid Crystals Azobenzenes and Related Mesogens Azomethine ( S chiff's Base) Mesogens Stable Phenyl, Biphenyl, Terphenyl, and Phenylethylbiphenyl Mesogens Ester Mesogens Derivatives of Chiral Alcohols Type II Chiral Nematic Liquid Crystals Type IIa Twin Systems Using Chiral Flexible Spacers Type IIb Materials Using Achiral Flexible Spacers and Chiral Terminal Groups Type IIc and d Materials Using One or Two Chiral Cores Type III Chiral Nematic Liquid Crystals Cholesteryl Esters Chiral Mesogens Derived from Cyclohexane Chiral Heterocyclic Mesogens Axially Chiral Liquid Crystals Axially Chiral Alkenes and Overcrowded Alkenes Allenes Tricyclo[4.4.0.0 3,8 ]decane or Twistane Derived Mesogens Sterically Hindered Biphenyl Derivatives Spirobiindane Derivatives Concluding Remarks

Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments

“…From an abundance of experimental studies on these chiral phases, two general trends emerged and were reviewed by Goodby et al . and others. , The key findings were the following: First, increasing the length of terminal aliphatic chains appended to a chiral center positioned at the core-chain juncture diminishes the effects of chirality with increasing chain length. The chiral center is described as increasingly buried in the overall structure, thereby diluting the effect of the chiral center by increasing the relative size (volume) of the aliphatic molecular substructure, especially in smectic layers.…”

Enantioselective Synthesis of 3-Aryl-3-hydroxypropanoic Esters as Subunits for Chiral Liquid Crystals

“…Chirality, i.e., the geometric property of an object not being superimposable on its mirror image, is an important research topic in a wide range of scientific and technological areas, especially in soft materials due to their huge potential for applications in diverse fields. − Liquid crystals (LCs) are dynamic functional soft materials that share the anisotropic properties of the crystalline state and the fluidity of a liquid. The molecular shape, microsegregation of incompatible parts, and specific molecular interactions drive the process of self-assembly and self-organization toward the formation of various LC phases. , The introduction of chirality into LCs results in various chiral liquid crystalline phases such as the cholesteric, chiral smectic, twist grain boundary (TGB), and blue phases (BP), each with unique properties. , Emerging new technologies based on chiral LCs (e.g., smart windows, biosensors, 3D tunable lasers) highlight the need to design and engineer new chiral molecules that self-assemble in predictable ways to produce materials that have desirable properties. ,, Despite the variety of the known chiral LC structures, chirality is mainly introduced by the incorporation of a readily available cholesterol unit − or chiral precursors bearing a methyl group at the chiral center. ,, Both chiral subunits suffer from several limitations. The structural variations of cholesterol-based materials are limited due to their monofunctional structure which allows extension only via esterification of the 3-hydroxy group, and there are no readily available racemic modifications.…”

“…The structural variations of cholesterol-based materials are limited due to their monofunctional structure which allows extension only via esterification of the 3-hydroxy group, and there are no readily available racemic modifications. Both limitations reduce the possibility for fine tuning the specific properties of the material and prevent comparison of the mesomorphic behavior between the enantiomer and the corresponding racemic mixture, which is not always unequivocal. , The chiral subunit with the methyl group at the stereogenic center is derived from either chiral alcohols or lactic acid, and it is often used in terminal chains or as a spacer of flexible dimer molecules. , The methyl group causes branching, which disrupts lateral interactions and destabilizes the LC behavior, which is particularly pronounced for bent-shaped dimers. , Since the LC behavior depends on the terminal chain length, the limited number of available adequate chiral alcohols represents a drawback to their use. Elongation of the terminal chain can be achieved only by the successive addition of a single carbon synthon which includes several synthetic steps .…”

Multicolor photonic patterns through an intensity-controlled single photopolymerization step

“…21,22 The composition of the mixtures was chosen such that a reflective colored coating in the visible spectrum was obtained, but in principle any color is possible by varying the chiral dopant concentration. 23 The mixture was dissolved in cyclopentanone as a solvent to enable gravure, roll-to-roll printing, and a surfactant (0.1 wt%) was added to promote planar alignment at the coating-air interface. 24 The mixture was printed on a black flexible biaxially oriented polyethylene terephthalate (PET) substrate, which supports the color contrast.…”