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Liquid Crystals

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.

Find all articles on liquid crystals in Wiley Online Library...

See the International Liquid Crystal Society's website.

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Thorsten Rieth, Tomasz Marszalek, Wojciech Pisula, Heiner Detert
Thermotropic Properties and Molecular Packing of Discotic Tristriazolotriazines with Rigid Substituents [Full Paper]

Thermotropic Properties and Molecular Packing of Discotic Tristriazolotriazines with Rigid Substituents

Stars in a helix: Fluorescent tristriazolotriazines with dialkoxyaryl branches (see figure) were prepared, and their optical and thermotropic properties were studied. The discotic molecules form broad hexagonal columnar mesophases with small π-stacking distances. In the crystalline state, the columns are composed of a helical superstructure.

Chem. Eur. J. 2014, 20, No. 17, 5000-5006

Supramolecular Assemblies by Charge-Transfer Interactions between Donor and Acceptor Chromophores

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.

Angew. Chem. Int. Ed. 2014, 53, No. 08, 2038-2054

Helical Carbon and Graphite Films Prepared from Helical Poly(3,4-ethylenedioxythiophene) Films Synthesized by Electrochemical Polymerization in Chiral Nematic Liquid Crystals

Helical carbon and graphite films are prepared from helical poly(3,4-ethylenedioxythiophene) films with a tunable helical sense and degree of helicity as precursors. The precursor polymer films are synthesized through asymmetric electrochemical polymerization in chiral nematic liquid-crystal (LC) fields. The spiral morphologies of the precursors are retained in the present graphite films.

Angew. Chem. Int. Ed. 2014, 53, No. 06, 1659-1663

Uttam Manna, Yashira M. Zayas-Gonzalez, Rebecca J. Carlton, Frank Caruso, Nicholas L. Abbott, David M. Lynn
Liquid Crystal Chemical Sensors That Cells Can Wear [Communication]

Liquid Crystal Chemical Sensors That Cells Can Wear

I'm stuck on you: Droplet-based liquid crystal (LC) chemical sensors can be immobilized on living cells. The decorated cells can report in real time on the presence of toxins in surrounding culture media. The approach provides new principles for the design of droplet-based LC sensors as well as methods for the local detection and reporting of chemical agents that are difficult to achieve in cellular environments using free-floating LC droplets.

Angew. Chem. Int. Ed. 2013, 52, No. 52, 14011-14015

Marco Bortolus, Karen Wright, Antonio Toffoletti, Claudio Toniolo, Anna Lisa Maniero
Self-Association of an Enantiopure β-Pentapeptide in Nematic Liquid Crystals [Full Paper]

Self-Association of an Enantiopure β-Pentapeptide in Nematic Liquid Crystals

Driving the self-assembly: Nematic liquid crystalline environments drive the reversible self-aggregation of a β-pentapeptide into oligomers with a well-defined structure. The inter- monomer distance distributions were obtained by electron paramagnetic resonance spectroscopy and this information enabled modeling of the oligomeric structures.

Chem. Eur. J. 2013, 19, No. 52, 17963-17968

Photodynamic Chiral Molecular Switches with Thermal Stability: From Reflection Wavelength Tuning to Handedness Inversion of Self-Organized Helical Superstructures

A good turn: Three compounds that bear two axially chiral bridged binaphthyl units were developed as photodynamic chiral dopants for nematic liquid crystals. For compounds with suitable bridge lengths, a change in the dihedral angle induced a switch of the binaphthyl units from the cisoid to the transoid form upon UV irradiation, which led to an inversion of the handedness of the helices.

Angew. Chem. Int. Ed. 2013, 52, No. 51, 13703-13707

Sebastian Polarz, Christian Bährle, Steve Landsmann, Alexander Klaiber
Panoscopic Structures by Hierarchical Cascade Self-Assembly of Inorganic Surfactants with Magnetic Heads Containing Dysprosium Ions [Communication]

Panoscopic Structures by Hierarchical Cascade Self-Assembly of Inorganic Surfactants with Magnetic Heads Containing Dysprosium Ions

Magnetic moustaches: Inorganic surfactants (I-SURFs) with head groups containing Dy3+ undergo a hierarchical self-organization cascade controlled by magnetic interactions. The resulting aggregates are shaped like dumbbells with frayed, moustache-like ends.

Angew. Chem. Int. Ed. 2013, 52, No. 51, 13665-13670

Kalman Toth, Jennifer K. Molloy, Micaela Matta, Benoît Heinrich, Daniel Guillon, Giacomo Bergamini, Francesco Zerbetto, Bertrand Donnio, Paola Ceroni, Delphine Felder-Flesch
A Strongly Emitting Liquid-Crystalline Derivative of Y3N@C80: Bright and Long-Lived Near-IR Luminescence from a Charge Transfer State [Communication]

A Strongly Emitting Liquid-Crystalline Derivative of Y3N@C80: Bright and Long-Lived Near-IR Luminescence from a Charge Transfer State

Great balls of fire: C60 and Y3N@C80 were connected to the same oligo(phenyleneethynylene) unit to investigate their structural and photophysical properties. NMR investigations revealed a fulleroid structure for the Y3N@C80 derivative, and both dyads gave rise to columnar phases with core-shell cylinders. The black and gray spheres represent the fullerene core units of the Y3N@C80 derivative, which is an ideal candidate to be involved in energy and electron transfer processes.

Angew. Chem. Int. Ed. 2013, 52, No. 47, 12303-12307

Sandra Gomez-Esteban, Marco Pezella, Angel Domingo, Gunther Hennrich, Berta Gómez-Lor
Solvent-Dependent Truxene-Based Nanostructures [Full Paper]

Solvent-Dependent Truxene-Based Nanostructures

Assembly line: Truxene derivatives self-assemble in solution and are able to gelate different solvent mixtures despite not having groups able to establish strong directional interactions (see figure). By taking advantage of the balance between molecule–molecule and molecule–solvent interactions, it is possible to control the final morphology of the resulting structures from fibrous superstructures to nanospheres.

Chem. Eur. J. 2013, 19, No. 47, 16080-16086

Markus Mansueto, Wolfgang Frey, Sabine Laschat
Ionic Liquid Crystals Derived from Amino Acids [Full Paper]

Ionic Liquid Crystals Derived from Amino Acids

Ionic liquid crystals from amino acids: Novel chiral amino acid derived imidazolium salts with amine or amide units were prepared through the sulfamidate. Depending on the steric bulk of the R group, the chain lengths and the type of anion X, stable SmA phases were detected (see scheme; Bn=benzyl).

Chem. Eur. J. 2013, 19, No. 47, 16058-16065

Thanh-Dinh Nguyen, Kevin E. Shopsowitz, Mark J. MacLachlan
Mesoporous Silica and Organosilica Films Templated by Nanocrystalline Chitin [Full Paper]

Mesoporous Silica and Organosilica Films Templated by Nanocrystalline Chitin

Organized nanomaterials: Nanocrystalline chitin (NCh) prepared by sequential deacetylation and hydrolysis of chitin fibrils isolated from king crab shells has been used to template mesoporous silica and organosilica (see figure). The large, crack-free films accurately replicate the organization of the NCh films originating from a transcription of the layered nematic phase of NCh.

Chem. Eur. J. 2013, 19, No. 45, 15148-15154

Joel A. Kelly, Amber M. Shukaliak, Clement C. Y. Cheung, Kevin E. Shopsowitz, Wadood Y. Hamad, Mark J. MacLachlan
Responsive Photonic Hydrogels Based on Nanocrystalline Cellulose [Communication]

Responsive Photonic Hydrogels Based on Nanocrystalline Cellulose

All in order: The self-assembly of nanocrystalline cellulose (NCC) with hydrogel precursors leads to nanocomposites with long-range chiral nematic order. The combination of chiral structure and hydrogel swelling behavior gives rise to iridescence that rapidly responds to various stimuli.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8912-8916

Mostofa K. Khan, Michael Giese, Marcus Yu, Joel A. Kelly, Wadood Y. Hamad, Mark J. MacLachlan
Flexible Mesoporous Photonic Resins with Tunable Chiral Nematic Structures [Communication]

Flexible Mesoporous Photonic Resins with Tunable Chiral Nematic Structures

Colors of nature: Mimicking of the structural colors of nature was achieved by the preparation of easily accessible chiral nematic polymer composites based on phenol–formaldehyde resins templated by cellulose nanocrystals. Removal of the template led to mesoporous polymer films with unique optical and physical properties. The potential application of these materials in optical sensors was also demonstrated.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8921-8924

Thomas Geelhaar, Klaus Griesar, Bernd Reckmann
125 Years of Liquid Crystals—A Scientific Revolution in the Home [Essay]

125 Years of Liquid Crystals—A Scientific Revolution in the Home

Patterns of communication: Reinitzer's discovery of liquid crystals in 1888 was followed by 30 years of scholarly dispute. One hundred years later, Pierre-Gilles de Gennes was awarded the Nobel Prize in Physics for his contribution to this scientific revolution. The commercial success of liquid crystals was achieved in display applications. Today more than 4 billion people use them in mobile communication devices. Painting: Detail from Raphael's School of Athens fresco.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8798-8809

Liquid-Crystalline Ordering as a Concept in Materials Science: From Semiconductors to Stimuli-Responsive Devices

Activity from order: Liquid-crystalline materials (see picture; blue) are formed from anisotropic molecules. They are used in liquid-crystal displays (LCDs), the prototype of flat-panel displays. Moreover, the combination of order and mobility in these phases allows the realization of mechanical actuators (green) or the improvement of materials for organic electronics (red).

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8810-8827

Xiaoming He, Jian-Bin Lin, Wang Hay Kan, Thomas Baumgartner
Phosphinine Lipids: A Successful Marriage between Electron-Acceptor and Self-Assembly Features [Communication]

Phosphinine Lipids: A Successful Marriage between Electron-Acceptor and Self-Assembly Features

A push in the right direction: An electron-accepting organophosphorus system has been combined with self-assembly features to create a strongly electron-accepting liquid-crystalline material (see picture). The stability and behavior of the self-assembled liquid crystal could be controlled by adjusting weak intermolecular forces, such as hydrogen bonding and π–π interactions.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8990-8994

Development of Structural Complexity by Liquid-Crystal Self-assembly

Liquid crystals on the way to complexity: Recent developments in liquid-crystalline materials have lead to new structures with enhanced complexity, including honeycombs and multicompartment structures, vesicular phases, and periodic and quasiperiodic arrays. New properties emerge, such as ferroelctricity and spontaneous achiral symmetry-breaking.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8828-8878

Yannian Li, Mengfei Wang, Timothy J. White, Timothy J. Bunning, Quan Li
Azoarenes with Opposite Chiral Configurations: Light-Driven Reversible Handedness Inversion in Self-Organized Helical Superstructures [Communication]

Azoarenes with Opposite Chiral Configurations: Light-Driven Reversible Handedness Inversion in Self-Organized Helical Superstructures

On the other hand: Azoarene compounds with axially chiral binaphthyl units of the same and opposite chiral configurations were doped into achiral liquid crystals (LCs). They were found to efficiently induce self-organized helical superstructures, which could be reversibly tuned by light irradiation using transcis photoisomerization to change the handedness of the helix (see scheme) in LC hosts.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8925-8929

Hemant Gopee, Andrew N. Cammidge, Vasily S. Oganesyan
Probing Columnar Discotic Liquid Crystals by EPR Spectroscopy with a Rigid-Core Nitroxide Spin Probe [Communication]

Probing Columnar Discotic Liquid Crystals by EPR Spectroscopy with a Rigid-Core Nitroxide Spin Probe

Discotics studied by EPR: The application of EPR spectroscopy to columnar discotic liquid crystals using a novel rigid-core nitroxide spin probe (see picture) is possible. EPR spectra measured at different temperatures across three phases of hexakis(n-hexyloxy)triphenylene show a strong sensitivity to the phase composition, molecular rotational dynamics, and columnar order.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8917-8920

Johanna R. Bruckner, Jan H. Porada, Clarissa F. Dietrich, Ingo Dierking, Frank Giesselmann
A Lyotropic Chiral Smectic C Liquid Crystal with Polar Electrooptic Switching [Communication]

A Lyotropic Chiral Smectic C Liquid Crystal with Polar Electrooptic Switching

A lyotropic analogue of the ferroelectric smectic C* phase has been found. The lyotropic smectic C* phase shows macroscopic chirality effects, such as a helical ground state and polarity-dependent electrooptic switching, thus indicating the presence of a spontaneous electric polarization. The helicity implies communication of the chiral director twist across the achiral solvent layers separating adjacent layers of the chiral mesogens.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8934-8937

Matthias Bremer, Peer Kirsch, Melanie Klasen-Memmer, Kazuaki Tarumi
The TV in Your Pocket: Development of Liquid-Crystal Materials for the New Millennium [Review]

The TV in Your Pocket: Development of Liquid-Crystal Materials for the New Millennium

Liquid refreshment: Over the past10 years liquid-crystal display (LCD) technology has been established as the leading display technology for televisions, PCs, and smartphones. The design of new materials to fulfill the stringent technical specifications with regard to electrooptical performance and reliability is getting more and more challenging, and the synthetic chemistry requires increasingly creative solutions.

Angew. Chem. Int. Ed. 2013, 52, No. 34, 8880-8896

Takahiro Ueda, Shiori Masuko, Fumito Araoka, Ken Ishikawa, Hideo Takezoe
A General Method for the Enantioselective Formation of Helical Nanofilaments [Communication]

A General Method for the Enantioselective Formation of Helical Nanofilaments

Controlling chirality: A general method to obtain homochiral helical nanofilaments (HNFs) based on a twisted nematic (TN) configuration was developed. By mixing bent-core molecules in the B4 phase with rod-like molecules in the nematic phase, the mixtures show the phase sequence of N–Bx(B4/N). Homochiral HNFs in the Bx phase were obtained from the mixtures when TN cells were cooled. The homochiral HNFs were observed by atomic force microscopy (see picture).

Angew. Chem. Int. Ed. 2013, 52, No. 27, 6863-6866

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