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(153) Production(s) de NOBILI M.
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Anchoring and gliding of a nematic liquid crystal on orienting photopolymers
Auteur(s): Nobili M.
Conference: Great Lakes photonics symposium (Dayton, USA, FR, 2006-06-12)
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Lyotropic mesophases in the thermotropic 5CB liquid crystal
Auteur(s): Toquer Guillaume, Porte Grégoire, Nobili M., Appell Jacqueline, Blanc C.
Conference: 21 th International Liquid Crystal Conference (Keystone, USA, FR, 2006-07-02)
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Static friction driven dynamics of surface walls and nematic disclinations on a rough surface
Auteur(s): Angot E., Blanc C., Nespoulous Mathieu, Nobili M.
Conference: 21 th International liquid crystal conference (Keystone, USA, FR, 2006-07-02)
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Chiral Free-standing Film Micromotor 
Auteur(s): Blanc C., Lorman V., Goc F., Nobili M.
Conference: The 21st International Liquid Crystal Conference (Keystone, US, 2006-07-02)
Ref HAL: hal-00326961_v1
Exporter : BibTex | endNote
Résumé: Symmetry arguments show that a flow of matter through a chiral medium can induce a collective molecular rotation. We report the study of such a linear coupling between a gas flow and molecular motion in thick free standing films of SmC* liquid crystal. This effect could be used to develop liquid crystalline micromotors potentially useful for microfluidics and micromechanics. Typical evolving target patterns have been recently observed by Tabe et al. [1] in a Langmuir monolayer of chiral liquid crystal molecules deposited on glycerol. We designed a more robust system composed of a free standing film of chiral molecules, without any liquid substrate. The flow of gas through the film is tuned by controlling the gas chemical potential. Direct pattern observation needs no Brewster angle microscope and is done under optical polarizing microscope. The whole set-up allows a quantitative study of the flow/rotation coupling phenomenon. The system shows a very rich spatio-temporal behavior. Here we focus on patterns obtained in a film suspended on a circular frame. In this geometry, a steady-state is attained where a spiral pattern is formed (see fig.1). We obtain the set of equations which govern the dynamics of the film under the gas flow. In a particular case, the equations involve only the c-director dynamics [2]. In the steady-state regime, they reduce to the competition of the elastic torque and an external torque induced by the flow. The observed static spiral patterns confirm the existence of such an external torque.
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X-Ray and Electrooptical Studies of Liquid Crystal Siloxane with a de Vries SmA* Phase
Auteur(s): Goc F., Blanc C., Lorman V., Nobili M., Samaritani S., Galli G., Kuczynski W.
(Article) Publié:
Ferroelectrics, vol. 343 p.101-110 (2006)
DOI: 10.1080/00150190600962176
WoS: 000242347100012
6 Citations
Résumé: We present the X-ray diffraction, polarizing optical microscopy and electrooptic response studies of the chiral liquid crystal siloxane DSi3-MR11 [1] with a de Vries-type behavior. In a wide temperature range (b.Delta T sim 50°C) the material shows no layer shrinkage but a weak nearly linear layer spacing variation with temperature. Neither discontinuity nor slope change occurs at the SmA*-SmC* transition. In addition, using the X-ray data, the unusual electrooptic response in both 1st and 2nd harmonics together with known thermal behavior of birefringence, we evidence the cross-over from the classical orthogonal to the de Vries-like SmA* regime in DSi3-MR11 siloxane.
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Cracks and topological defects in lyotropic nematic nanotube gels.
Auteur(s): Islam M.F., Nobili M., Fanghu Y., Lubensky T.C., Yodh A.G.
(Article) Publié:
Physical Review Letters, vol. 95 p.148301 (2005)
Résumé: We report on the effects of the coupling of nematic order and elasticity in anisotropic lyotropic gels consisting of large nematic domains of surfactant coated single wall carbon nanotubes embedded in a cross-linked N-isopropyl acrylamide polymer matrix. We observe the following striking features: (i) undulations and then cusping of the gel sidewalls, (ii) a nematic director field that evolves as the gel sidewalls deform, (iii) networks of surface cracks that are orthogonal to the nematic director field, and (iv) fissures at the sidewall cusps and associated topological defects that would not form in liquid nematics.
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Etude structurale d'un système mixte thermotrope-lyotrope.
Auteur(s): Toquer Guillaume, Porte Grégoire, Nobili M., Blanc C.
Conference: 12ième Colloque Francophone sur les Cristaux Liquides. (Montpellier, France, FR, 2005-09-13)
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