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Étude des propriétés de polymères cristaux liquides en peigne en optique non linéaire.

Abstract : Many studies have been carried out to realize organic materials for Non Linear Optics (NLO). In such materials, polarizable aromatic pendant side groups are grafted on the macromolecular chain, and the resulting polymer is poled under a strong DC electric field.The originality of my doctoral research project was to use polymers of the same type, but possessing a liquid crystalline character and to show that the axial ordering of the mesophases could be used to enhance field-induced polar ordering. Four polymers bearing the same NLO mesogenic group (the oxi-4-4'-cyanobiphényl OCB) have been studied, namely two copolyethers A and B, a polyacrylate C, and a polymethacrylate D. A and C are liquid crystalline, whereas B and D are isotropic at rest. The microscopic and macroscopic parameters of the system have been carefully measured, in order to compare the experimental results to the theoretical models. I showed that polymers B and D can be pulled through the N/isotropic transition by the electric field. The liquid crystalline polymers A and C are much more efficient than the conventional materials (19pm/V at 1.06um for polymer C after relaxation), and their behavior is in good agreement with the statistical models. In the liquid crystalline polymers A and C the coefficient is enhanced by a factor of about three.
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Submitted on : Tuesday, September 14, 2021 - 2:23:26 PM
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  • HAL Id : tel-01322812, version 1

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Dominique Gonin Peysson. Étude des propriétés de polymères cristaux liquides en peigne en optique non linéaire.. Polymères. Université Paris 6, 1994. Français. ⟨tel-01322812⟩

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