Design of liquid crystals: from a nematogen to thiophene-based π-conjugated mesogens

Abstract

It is fundamentally important to study the relationships between structures and properties of liquid crystals. Professor G.W. Gray developed new rod-like nematic liquid crystals, 4-alkyl-and 4-alkoxy-4ʹ-cyanobiphenyls, which act as materials for stable informational liquid crystal displays. This molecule was invented based on his deep understanding of the relationships of chemical structure and physical properties of liquid crystals. After the discovery of nematogenic liquid crystals for display application, the advent of the molecular design and synthesis of liquid crystals has produced a variety of new family of functional liquid crystals. For example, as a new twist of rigid rod mesogens, oligothiophene rings have emerged recently. Due to their extended π-conjugated systems, oligothiophene-based liquid crystals exhibit various electronic and optical functions. In this review, we describe the impact of Professor Gray's nematic liquid crystals as well as the structures and functions of oligothiophene-based liquid crystals.

Ethylenedioxythiophene as a novel central unit for bent-core liquid crystals

“…Fourier transform infrared spectroscopy (FT-IR) spectra were recorded using Shimadzu -8400; only major peaks are reported in cm −1. 1 H Nuclear magnetic resonance spectroscopy (NMR) and 13 (6) were prepared following the method described in literature [36,37].…”

“…[19][20][21][22][23]. While a number of BC LC derived from simple thiophene central unit are known [5][6][7][8][9][10][11][12][13][14][15], extensive literature search reveals that any BC LC derived from EDOT has so far not been realised.…”

“…Incorporation of five-member heterocyclic compounds widens the bent angle and show extensive mesomorphic behaviour [4]. A number of 2,5-disubstituted thiophene-based liquid crystal compounds have been synthesised and investigated their structural properties [5][6][7][8][9][10][11][12][13][14][15]. The sulphur heteroatom containing central core can substantially enhance optical anisotropy, fast switching time, reduction in viscosity, elevation of a negative dielectric anisotropy and lowering melting points, which make them good candidates for technological importance [16][17][18].…”

Chiral Liquid Crystalline Electronic Systems

“…As shown in Figure 2, triphenylene, hexabenzocoronene, phthalocyanine, perylene bisimide derivatives are known as columnar LC semiconductors [12][13][14][15][16]. Phenylnaphthalene and oligothiophene derivatives exhibit good carrier transport properties in smectic phases [17][18][19][20][21]. The application of LC semiconductors to electroluminescence device [6,22], field effect transistors [5,[23][24][25][26][27], and solar cells have been investigated [28][29][30].…”

Liquid-crystalline perylene bisimide derivatives bearing an azacrown ether ring complexing with alkaline metal ions

“…15 Liquid crystalline (LC) materials based on extended π-conjugated units work as semiconductors and anisotropic electronic charge carrier transports have been studied extensively. 16–18 In the LC semiconductors, long-range transport of electronic charge carriers through intermolecular overlaps between π-conjugated units has been confirmed, due to one- or two-dimensional self-organization of the π-conjugated units in the LC phases. 19–24 The LC semiconductors have been applied to electroluminescence devices, field effect transistors, and solar cells.…”