Liquid crytals (LCs) are probably the most exciting state of matter. They attract scientists across disciplines such as chemistry, physics, materials science, and engineering—theorists and experimentalists alike. These days, you can buy quite affordable LCD TV sets around the corner, but that's just one of the many things liquid crystals can do. The selection of recent research articles presented below illustrates the broad interest in this area of soft condensed matter.
J. W. Goodby, P. J. Collings, T. Kato, C. Tschierske, H. Gleeson,
Handbook of Liquid Crystals
2nd edition, Wiley-VCH, Weinheim, 2014.
Find all articles on liquid crystals in Wiley Online Library...
See the International Liquid Crystal Society's website.
B planar, B aligned: A planarized triphenylborane, bearing three 3,4,5-tridodecyloxyphenyl groups, forms a hexagonal columnar liquid-crystalline phase at ambient temperature. It has a columnar π-stacked structure and ambipolar carrier-transport properties with hole- and electron-mobility values of 3×10−5 cm2 V−1 s−1 and approximately 10−3 cm2 V−1 s−1, respectively.
A new series of selenide and diselenide liquid crystals containing cholesterol were synthesized and characterized. Most of the materials presented good thermal stability with SmC* and SmA* phases over a wide temperature range. The prepared diselenides also have potential biological applications, and they showed good antioxidant properties.
The curious incident of the mesogen in the twist–bend nematic phase: A large number of new materials that exhibit the “twist–bend nematic phase” have been prepared, allowing several trends between structure and liquid-crystalline behaviour to be found.
Three in one: A series of toroidal cyclo-2,9-tris-1,10-phenanthroline macrocycles with a unique hexaaza cavity are reported (see figure). Yamamoto aryl–aryl coupling is a versatile tool for the cyclotrimerization of functionalized 1,10-phenathroline precursors. For the first time, the liquid crystallinity and self-assembly on surfaces could be studied for a macrocycle of the torand family.
Smectic porphyrins: The replacement of two meso-aryl groups of porphyrins with phenylethynyl or naphthylethynyl substituents increases the melting points of the resultant porphyrins by ∼100 °C and has allowed thermotropic liquid crystallinity to be demonstrated, including a unique switch from columnar to smectic phase.
On the same side: Dinaphthopyrene-diimides derived from 1,8-disubstituted pyrene, with both substituents on the same side, stack into columns to form hexagonal and rectangular liquid crystals and thus fully function as semi-flexible self-assembling disks (see figure). In contrast, their centrosymmetric isomers derived from 1,6-disubstituted pyrene are less prone to form liquid crystals.
Horn section: Silver ion-triggered metallogelation of a solution of p-pyridyl-appended oligo(p-phenylenevinylene) (OPV)-based scaffolds comprising uniformly dispersed single-walled carbon nanohorns (SWCNHs) is reported. Aging of the metallogel results in the formation of a trihybrid gel comprising nanoscale metal–organic particles (NMOPs), SWCNHs, and in situ generated silver nanoparticles (AgNPs) (see figure).
Come into my arms: Stilbenoid star-shaped mesogens pack densely, in helical structures that have a short correlation length, in columnar liquid-crystal phases. Attaching a fullerene guest to the interior of the star fills the void space between the arms and considerably increases the mesophase stability by approximately 70 °C. The stabilization is the result of the formation of a fullerene triple helix.
Liquefying DNA: A series of solvent-free DNA melts that exhibit both liquid-crystal ordering and melting into isotropic liquids have been generated by electrostatic complexation of DNA with surfactants. Stable smectic mesophases and liquid phases are obtained in the −20 °C to 200 °C temperature range without thermal degradation of the DNA.
Mesogenic core-extended perylenes: Tetracarboxy-substituted dinaphthoperylenes are obtained from perylene through regiospecific Friedel–Crafts diglyoxylation. Whereas the n-alkyl esters only show monotropic mesomorphism and racemically branched alkyl esters fail to show any mesophase, swallow-tailed alkylimides exhibit astonishingly robust liquid crystalline self-assembly (see figure).
Out of the woods: Novel mesoporous and nanostructured materials can be generated by templating approaches based on cellulose-based liquid crystals derived from trees. This Review focuses on materials templated by cellulose nanocrystals, since their chiral nematic order allows their use in various optical applications such as optical filters, sensors, and optoelectronics.
Di- and tricationic organic salts combine the properties of corresponding monocationic salts with individual features due to the presence of different charged heads on the cation structures. This allows their use in different fields of application such as ionic liquid crystals and gel phases.
Riot of color: Alternate stacking of aromatic donor and acceptor building blocks by complementary and directional charge-transfer interactions produce versatile supramolecularly assembled materials including micelles, vesicles, nanotubes, fibrillar gels, folded polymers, cross-linked networks, and liquid-crystalline phases.