J. Ortega

University of the Basque Country

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J. Etxebarría

University of the Basque Country

C. L. Folcia

University of the Basque Country

M. Blanca Ros

Universidad de Zaragoza

Josu Martínez-Perdiguero

University of the Basque Country

Nélida Gimeno

Donostia International Physics Center

I. Alonso

University of the Basque Country

José Luís Serrano

Universidad de Zaragoza

Pablo Espinet

Universidad de Valladolid

Teresa Sierra

Instituto de Nanociencia y Materiales de Aragón

T. Bręczewski

University of the Basque Country

Cooperative Institutions

Universidad de Zaragoza

University of the Basque Country

Consejo Superior de Investigaciones Científicas

Centre National de la Recherche Scientifique

Instituto de Nanociencia y Materiales de Aragón

Universidad de Valladolid

Universidad Autónoma de Madrid

Centro Médico Sanitas Zaragoza

University of Colorado Boulder

University of Minnesota

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The SmA phase of a bent-core V-shaped compound: structure and electric-field response

Liquid Crystals (2010)

I. Alonso Josu Martínez-Perdiguero J. Ortega C. L. Folcia J. Etxebarría

The smectic A (SmA) phase of a V-shaped mesogen with a molecular bending angle of 60° was studied. According to X-ray measurements, the molecules are arranged with the ‘bow-string’ direction parallel to the smectic layer. This point was confirmed by birefringence analysis and the result is compatible with a non-polar structure. A detailed study of the (001) smectic layer reflection versus temperature was also carried out to determine the smectic translational order parameter. The results indicate that the material presents a high degree of translational order. In addition, the electric field response of the material was studied by means of second harmonic generation. This technique turned out to be highly sensitive to small structural distortions due to the V-shape of the constituent molecules.

Mesogen

10.1080/02678292.2010.521858

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Citations (12)

Second harmonic generation with metal‐containing ferroelectric liquid crystals

Advanced Materials (1996)

Pablo Espinet J. Etxebarría C. L. Folcia J. Ortega M. Blanca Ros

The second harmonic generation (SHG) parameters for metal‐containing ferroelectric liquid crystals are reported for the first time. Some of the materials, based on the structure shown in the Figure, exhibit reasonable NLO efficiencies despite the fact that the molecules themselves do not possess well‐defined donor–acceptor arrays. magnified image

Acceptor

10.1002/adma.19960080909

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Citations (29)

Polar Switching in a Lyotropic Columnar Nematic Liquid Crystal Made of Bowl‐Shaped Molecules

Advanced Materials (2015)

Julia Guilleme Emma Cavero Teresa Sierra J. Ortega C. L. Folcia

A polar response in a lyotropic columnar nematic material is reported. The material accommodates bowl-shaped molecules with strong axial dipole moments in column segments without head-to-tail invariance. Optical second-harmonic-generation methods confirm that the nematic columns align unidirectionally under an applied electric field and the material develops remnant macroscopic polarization observable for hours. The switching takes place by a flip of the columns.

Lyotropic

Biaxial nematic

10.1002/adma.201500238

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Citations (32)

Comparison between the switching dynamics of homeotropic and planar cells of chiral smectic-Cliquid crystals

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics (2000)

N. Pereda J. Ortega C. L. Folcia J. Etxebarría

The molecular dynamics during the switching of homeotropic and planar cells of chiral smectic-C liquid crystals has been investigated using electrooptic measurements and second-harmonic-generation interferometry. Two ferroelectric liquid crystals with great differences in their molecular structures have been studied. It has been found that the molecular motion is rather different depending on the type of cell used. For planar cells, the azimuthal rotation of the molecules is limited within half the smectic cone and the molecules rotate in opposite directions in the two halves of the chevron structure. In contrast, for homeotropic cells there is no chevron structure and a uniform macroscopic optical indicatrix can be defined all over the sample during the whole switching process. However, the molecular reorientation takes place within numerous microdomains of size smaller than the optical wavelength. There are two types of microdomains that occur with different probabilities depending on the material. Within each domain the molecules rotate in opposite directions, and the molecules describe a complete cone during a whole switching period.

Homeotropic alignment

Antiferroelectricity

10.1103/physreve.62.2334

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Citations (1)

Second harmonic generation by micropowders: a revision of the Kurtz–Perry method and its practical application

Applied Physics B (2013)

I. Aramburu J. Ortega C. L. Folcia J. Etxebarría

Particle (ecology)

Harmonic

10.1007/s00340-013-5678-9

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Citations (37)

Second harmonic generation and symmetry of SrS₂O₆ · 4H₂O

Zeitschrift für Kristallographie - Crystalline Materials (2000)

Etelvina de Matos Gomes E. Nogueira M. Belsey F. J. Zúñiga J. Etxebarría

We show that although the crystalline structure of Strontium Dithionate Tetrahydrate can be well described in either P6 4 and P3 1 space groups (or respectively, P6 2 and P3 2 ) and electro-optic measurements have indicated the 32 point group, optical second harmonic measurements performed on an oriented crystal are only compatible with point group 3.

Tetrahydrate

Space group

Crystal (programming language)

10.1524/zkri.2000.215.4.222

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Citations (0)

Novel liquid-crystalline mesogens and main-chain chiral smectic thiol-ene polymers based on trifluoromethylphenyl moieties

Journal of Materials Chemistry (2009)

Hong Yang Lixing Wang Renfan Shao Noel A. Clark J. Ortega

The synthesis and characterization of a series of novel liquid-crystalline molecules containing a trifluoromethylphenyl core or a 2,3-bis(trifluoromethyl)phenyl core is described. All trifluoromethylphenyl-containing compounds (W530, W551, and W558) have mesomorphic properties while 2,3-bis(trifluoromethyl)phenyl-containing compounds (W555, W556, W557) are room-temperature crystals without mesophases. Thereafter, based on the chemical structure of W558, to pursue a mesogen with a large electroclinic effect in the SmA* phase for development into electromechanical actuators, a chiral smectic thiol-ene monomer (K0901) is synthesized and polymerized in organic solvents. The polymer is characterized by GPC, DSC, PLM, XRD and shows an expected I–SmA* –Glass phase sequence though the electroclinic effect is relatively small.

Mesogen

Ene reaction

10.1039/b907907f

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Citations (30)

Synergistic π–π and Pt–Pt interactions in luminescent hybrid inorganic/organic dual columnar liquid crystals

Journal of Materials Chemistry C (2015)

Emiliano Tritto Rubén Chico J. Ortega C. L. Folcia J. Etxebarría

Hybrid inorganic/organic dual columnar materials display aggregation-induced enhanced phosphorescence based on inter-disk Pt–Pt interactions in a fluid state.

Columnar phase

10.1039/c5tc01802a

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Citations (21)

Thermally induced light-scattering effects as responsible for the degradation of cholesteric liquid crystal lasers

Optics Letters (2015)

J. Etxebarría J. Ortega C. L. Folcia Gerardo Sanz-Enguita I. Aramburu

We have studied the degradation process of the laser emission in a cholesteric liquid crystal laser. We have found that there exists a negative correlation between the laser efficiency and the amount of light scattered by the liquid-crystal sample in the illuminated area. The growth of scattering is attributed to the appearance of small imperfections generated in the sample as a result of certain thermal processes that involve the dye molecules. The scattering implies an increase of the coefficient of distributed losses, which is the main response of the rise of the laser threshold.

Cholesteric liquid crystal

Degradation

Crystal (programming language)

10.1364/ol.40.001262

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Citations (16)

H-Bonded Donor–Acceptor Units Segregated in Coaxial Columnar Assemblies: Toward High Mobility Ambipolar Organic Semiconductors

Journal of the American Chemical Society (2016)

Beatriz Feringán Pilar Romero José Luís Serrano C. L. Folcia J. Etxebarría

A novel approach to ambipolar semiconductors based on hydrogen-bonded complexes between a star-shaped tris(triazolyl)triazine and triphenylene-containing benzoic acids is described. The formation of 1:3 supramolecular complexes was evidenced by different techniques. Mesogenic driving forces played a decisive role in the formation of the hydrogen-bonded complexes in the bulk. All of the complexes formed by nonmesogenic components gave rise to hexagonal columnar (Colh) liquid crystal phases, which are stable at room temperature. In all cases, X-ray diffraction experiments supported by electron density distribution maps confirmed triphenylene/tris(triazolyl)triazine segregation into hexagonal sublattices and lattices, respectively, as well as remarkable intracolumnar order. These highly ordered nanostructures, obtained by the combined supramolecular H-bond/columnar liquid crystal approach, yielded donor/acceptor coaxial organization that is promising for the formation of ambipolar organic semiconductors with high mobilities, as indicated by charge transport measurements.

Ambipolar diffusion

Triphenylene

Discotic liquid crystal

Acceptor

Organic semiconductor

Columnar phase

10.1021/jacs.6b06792

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Citations (72)