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.
Although discotic liquid crystals are attractive functional materials, their use in elec¬tronic devices is often restricted by high melting and clearing points. Among promising candidates for applications are crown-5 ether based liquid crystals with peripheral n-alkoxy side chains, which, however, still have melting points above room temperature. To overcome this problem, a series of o-terphenyl and triphenylene crown-5 ether derivatives was prepared in which δ-methyl branched alkoxy side chains of varying lengths substitute the peripheral linear alkoxy chains. The mesomorphic properties of the novel crown ethers were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction.δ-Methyl branching indeed lowers melting points resulting in room temperature hexagonal columnar mesophases. The mesophase widths, which ranged from 87 K to 30 K for o-terphenyls, significantly increased to 106-147 K for the triphenylenes depending on the chain lengths, revealing the beneficial effect of the flat mesogen due to improved π-π interactions.
Sabine Laschat, Jochen Kirres, Friederike Knecht, Philipp Seubert, Angelika Baro
ChemPhysChem, February 08, 2016, DOI: 10.1002/cphc.201501166. Read article
The structural organization and evolution of the organic semiconducting molecule 2,7-dioctyloxybenzothieno[3,2-b]-benzothiophene on a soft matrix is studied. Thin films of a blend formed by polystyrene and the molecule were prepared by spin coating onto a silicon substrate, and studied by a combination of microscopy and scattering techniques. The organic semiconducting molecule segregated to the surface and developed a phase with structure different from the bulk one, as in the case of a "substrate" induced phase observed previously. Under solvent vapor annealing procedure the growth of micrometer sized tetragonal crystals onto the polymer surface was observed, not evidenced on silicon substrates.
DANIELE MARTINEZ-TONG, Christian Ruzié, Yves H Geerts, Michele Sferrazza
ChemPhysChem, February 08, 2016, DOI: 10.1002/cphc.201501144. Read article
Unprecedented, reversible, and dynamic control over the assembly of gold nanorods dispersed in liquid crystals (LC) is demonstrated. The LC director field is dynamically tuned at the nanoscale using microscale ring confinement through the interplay of elastic energy at different temperatures, thus fine-tuning its core replacement energy to reversibly sequester nanoscale inclusions at the microscale. This leads to shifts of 100 nm or more in the surface plasmon resonance peak, an order of magnitude greater than any previous work with AuNR composites.
Elaine Lee, Yu Xia, Robert C. Ferrier, Hye-Na Kim, Mohamed A. Gharbi, Kathleen J. Stebe, Randall D. Kamien, Russell J. Composto, Shu Yang
Adv. Mater., February 08, 2016, DOI: 10.1002/adma.201506084. Read article
Liquid crystals may help to fabricate self-assembled anisotropic photonic materials from tailored DNA origami nanostructures. First results show that films of respective nanocomposites can be uniformly aligned with their optical axis parallel or perpendicular to the substrate. In addition, a decoration phenomenon visualizing the liquid crystal director field is found to appear on graphene substrates.
Kevin Martens, Timon Funck, Susanne Kempter, Eva-Maria Roller, Tim Liedl, Benno M. Blaschke, Peter Knecht, José Antonio Garrido, Bingru Zhang, Heinz Kitzerow
Small, February 05, 2016, DOI: 10.1002/smll.201503382. Read article
A new liquid crystalline ion gel exhibits unprecedented properties: conductivity up to 8 mS cm−1, thermal stability to 300 °C, electrochemical window to 6.1 V, as well as adjustable transport anisotropy (up to 3.5×) and elastic modulus (0.03–3 GPa). The combination of ionic liquid and magnetically oriented rigid-rod polyanion provides widely tunable properties for use in diverse electrochemical devices.
Ying Wang, Ying Chen, Jianwei Gao, Hyun Gook Yoon, Liyu Jin, Maria Forsyth, Theo J. Dingemans, Louis A. Madsen
Adv. Mater., January 29, 2016, DOI: 10.1002/adma.201505183. Read article
Chains and phases: New meso-tetraaryl-substituted free-base porphyrins containing alkyl amide chains and their palladium(II) and platinum(II) complexes are prepared in good yields and fully characterized by polarized light optical microscopy (see figure) and differential scanning calorimetry. The number of terminal alkyl chains, their lengths, and the palladium(II) metal center play key roles in achieving mesomorphic behavior.
Nuno M. M. Moura, Cristián Cuerva, José A. S. Cavaleiro, Ricardo F. Mendes, Filipe A. Almeida Paz, Mercedes Cano, M. Graça P. M. S. Neves, Carlos Lodeiro
ChemPlusChem, January 28, 2016, DOI: 10.1002/cplu.201500557. Read article
You′re twisting my melon, man! The first example of a liquid-crystalline oligomer to exhibit the twist-bend nematic phase (NTB/NX) is described, providing new insights into spontaneous symmetry breaking in achiral fluids.
Richard J. Mandle, John W. Goodby
ChemPhysChem, January 25, 2016, DOI: 10.1002/cphc.201600038. Read article
New methods and strategies to control molecular orientation for polymer thin films are proposed in this review. Moreover, they demonstrate the effectiveness and impact of the free surface in thin films on molecular orientation. The film surfaces have not been treated as a major subject to control molecular orientation. New methods were demonstrated for controlling the inner structures (molecular orientation) of polymer films from the surface/interface of thin films.
The Chemical Record, January 18, 2016, DOI: 10.1002/tcr.201500232. Read article
A simple modular design was used to impart liquid-crystalline properties to iridium complexes without modification of their photophysical properties. Annealed films of the liquid-crystalline complexes display hole mobilities up to three orders of magnitude higher than parent iridium complex without mesogenic groups and are the highest values reported to date for iridium complexes (see figure).
Yafei Wang, Christopher P. Cabry, ManJun Xiao, Louise Male, Stephen J. Cowling, Duncan W. Bruce, Junwei Shi, Weiguo Zhu, Etienne Baranoff
Chem. Eur. J., December 22, 2015, DOI: 10.1002/chem.201504669. Read article.
The high temperature magnetic and structural properties of an amphiphilic iron(III) spin crossover complex are reported. Thermal cycling reveals a scan rate-dependent 20 K thermal hysteresis close to room temperature. Differential scanning calorimetry and cross polarized microscopy are used to show that the magnetic switching aligns with a material change from solid to ordered liquid phase on warming.
Anthony J. Fitzpatrick, Paulo N. Martinho, Brendan J. Gildea, John D. Holbrey, Grace G. Morgan
Eur. J. Inorg. Chem., December 16, 2015, DOI: 10.1002/ejic.201501335. Read article.
Changing states: The cohesive free energy density concept (CFED) is applied to thermotropic cyanobiphenyl-based liquid crystals to establish predictive quantitative correlations between each antagonist segments of the amphiphilic molecules (flexible alkyl tail/rigid aromatic core) and their transition temperatures (solid→liquid crystalline/liquid crystalline→ isotropic liquid; see figure).
Thibault Dutronc, Emmanuel Terazzi, Laure Guénée, Kerry-Lee Buchwalder, Sébastien Floquet, Claude Piguet
Chem. Eur. J., December 14, 2015, DOI: 10.1002/chem.201503420. Read article.
Phosphoric acid and calcium nitrate self-assemble into lyotropic liquid crystalline mesophases that can be calcined into sponge-like transparent mesoporous thin films of calcium hydroxyapatite.
Ebrima Tunkara, Ömer Dag
Eur. J. Inorg. Chem., December 2, 2015, DOI: 10.1002/ejic.201501116. Read article.