Stéphane Méry

Centre National de la Recherche Scientifique

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Benoı̂t Heinrich

Institut de Physique et Chimie des Matériaux de Strasbourg

D. Guillon

Centre National de la Recherche Scientifique

Jean‐François Nicoud

Centre National de la Recherche Scientifique

Laure Catala

Institut de Chimie Moléculaire et des Matériaux d'Orsay

Nicolas Leclerc

Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé

Denis Haristoy

National Centre of Scientific Research "Demokritos"

Patricia Chávez

Escuela Superior Politecnica del Litoral

Sadiara Fall

Laboratoire des Sciences de l'Ingénieur, de l'Informatique et de l'Imagerie

Quentin Huaulmé

Systèmes Moléculaires et nanoMatériaux pour l'Énergie et la Santé

Pedro J. Sebastião

University of Lisbon

Cooperative Institutions

Centre National de la Recherche Scientifique

Université de Strasbourg

Institut de Physique et Chimie des Matériaux de Strasbourg

Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé

Institut de Chimie

Institut Européen de Chimie et Biologie

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Laboratoire de Chimie Organique

Département Santé des Plantes et Environnement

Ingenierie des Materiaux polymeres

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Antiferroelectric and ferrielectric liquid crystalline low molar mass materials and polymers

Liquid Crystals (1997)

Stéphane Méry D. Lötzsch G. Heppke R. Shashidhar

Novel liquid crystalline Low Molecular Mass (LMM) materials bearing two chiral lactate groups, as well as compounds of like structure to MHPOBC have been synthesized. All the LMM compounds exhibit the SmC*A (antiferroelectric) and/or SmC*gamma (ferrielectric) phases. The mesogens have been incorporated as pendant groups on polymer backbones of three different natures to prepare side chain liquid crystalline copolysiloxanes, homopolysiloxanes and homopolyacrylates. The investigation of the polymers by means of miscibility studies showed that the antiferro- and ferri-electric phases are strongly destabilized in the coposiloxanes and homopolysiloxanes, while in the homopolyacrylates a large temperature range mesophase is found to be miscible with the SmC*A phase. The physical properties of the mesophases and their stability, both for the LMM materials and the polymers, are presented and discussed.

Antiferroelectricity

Miscibility

Molar mass

10.1080/026782997207902

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Citations (28)

Rational Engineering of BODIPY‐Bridged Trisindole Derivatives for Solar Cell Applications

ChemSusChem (2017)

İbrahim Bulut Quentin Huaulmé Antoine Mirloup Patricia Chávez Sadiara Fall

Boron dipyrromethene (BODIPY) and its derivatives are known to be efficient photon-harvesting chromophores. However, their study as active materials in bulk heterojunction (BHJ) solar cells is still scarce. In this study, the development of new synthetic ways to design original BODIPY-based dumbbell-shape molecules, including a first 2,3,5,6-tetravinyl aromatic BODIPY molecule, is reported. High fill factors can be obtained in BHJ solar cells when blended with a fullerene derivative, leading to a new record BODIPY-based power conversion efficiency of 5.8 %.

BODIPY

Rational design

Molecular engineering

10.1002/cssc.201700465

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Citations (50)

Soft mode and related behaviour in the SmA and SmC* phases of a ferroelectric liquid crystalline polymer by dielectric spectroscopy

Liquid Crystals (2002)

Shyamal Kumar Kundu B. K. Chaudhuri Laure Catala Stéphane Méry

Anomalous dielectric relaxation behaviour is observed in the ferroelectric liquid crystalline polymer (viz. ferroelectric copolysiloxane (R)-COPS 11-10) around the ferroelectric SmC* to paraelectric SmA phase transition. Measurements have been performed on sample of thickness ∼10 μm in indium-tin-oxide coated cell in the frequency range 10 Hz to 13 MHz. With increase of temperature, a gradual shift of the soft mode frequency towards the higher frequency side was observed, while a decrease in the relaxation strength was seen with the corresponding increase in temperature. The shifts of the soft modes in the SmC* and SmA phase are considered to be due to change in the viscosity of the polymer, as an increase in viscosity increases fluctuations of the coupling between the dipoles in the network even far from the paraelectric-ferroelectric phase transition. Application of a bias field causes a shift of the critical frequency towards the higher frequency side, while the dielectric strength (δε) decreases under the bias field. The Cole-Cole fitting parameters obtained from the best fit of the dielectric constant data are found to be consistent with other similar materials. Another relaxation mode (molecular mode) was also observed which comes into play in both the smectic phases (SmC% and SmA) and contributes to the dielectric permittivity.

Soft modes

10.1080/02678290210133123

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Citations (12)

Ferroelectric side group liquid crystalline polysiloxanes containing a chiral sulphinate derivative

Liquid Crystals (1999)

Stéphane Méry Laure Catala Pedro J. Sebastião Benoı̂t Heinrich Jean‐François Nicoud

A series of chiral liquid crystalline homo- and co-polysiloxanes is reported, in which the chirality is introduced via an arenesulphinate moiety. All polysiloxanes were prepared by using three polymer-analogous reactions and exhibit the ferroelectric SmC* phase. In the series of copolymers, a high heterogeneity in the ratio of mesogenic pendants is observed and explains the existence of large biphasic regions at the phase transitions. A complete characterization of the ferroelectric properties was performed for the copolysiloxanes, and revealed high values of the spontaneous polarization.

Mesogen

Moiety

Chirality

Pendant group

10.1080/026782999203779

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Citations (8)

Nematic-nematic modification in side-on-fixed polysiloxanes

Liquid Crystals (1990)

F. Hardouin Stéphane Méry M. F. Achard M. Mauzac Patrick Davidson

Abstract A series of side-chain liquid crystal polymers has been synthesized with mesogenic groups laterally branched to a polysiloxane backbone (the so-called side-on-fixed). An anomaly of the diamagnetic anisotropy in the nematic state was shown to be very sensitive to a number of structural parameters such as the length of the aliphatic tails, the length of the spacer and the fixation rate of the mesogenic groups on the backbone. On the basis of accurate density measurements, microscopic observations and X-ray diffraction experiments on aligned samples, the occurrence of a nematic-nematic transition connected to this anomaly is questionned.

Mesogen

Side chain

Diamagnetism

Biaxial nematic

10.1080/02678299008047371

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Citations (45)

Structure and photoconductive behaviour of a sanidic liquid crystal

Liquid Crystals (2000)

Denis Haristoy Stéphane Méry Benoı̂t Heinrich L. Mager Jean‐François Nicoud

Abstract A series of [1]benzothieno[3,2-b][1]benzothiophene-2,7-dicarboxylate derivatives consisting of a flat, conjugated aromatic moiety containing sulphur hetero-atoms and substituted by terminal chains - ethyl, decyl, Z-4-decenyl or 2-(2-butoxyethoxy)ethyl - has been synthesized. These materials exhibit a smectic liquid crystalline phase, the stability of which was found to be strongly dependent on the length and the nature of the terminal chains. In the mesophase, the molecular arrangement within the smectic layer is characterized by a local stacking of the rigid parts similar to that found in discotic columnar systems. Finally, clear photoconductive behaviour was found in mechanically aligned samples of these liquid crystals.

Benzothiophene

Moiety

Photoconductivity

Discotic liquid crystal

Columnar phase

10.1080/026782900202769

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Citations (32)