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18 December 2002 Effects of the viscoelastic properties on the orientational dynamics of chromophores in low Tg guest-host polymers
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Abstract
In photorefractive guest-host polymers, fast orientational dynamics of push-pull chromophores are needed to obtain the so-called orientational enhancement as well as high performances. For this purpose, a better understanding of the relationships between viscoelastic properties of polymers and orientational processes of chromophores is now essential for the optimization and the development of new efficient photorefractive polymers. In the present investigation, the orientational dynamics of the chromophores are probed in details by dielectric spectroscopy, second-harmonic generation and ellipsometric techniques, in various doped polymers. The materials are based on a polyvinylcarbazole plasticized with N-ethyl carbazole, a polysiloxane functionnalized with a carbazole pendant, as well as polystyrenes with different average macromolecular weights. The temperature-dependencies of their dielectric and electro-optic responses provide information on the rotational mobility of the chromophores at a microscopic scale. These data are directly compared to the temperature-dependence of the viscoelastic properties, characterized at a macroscopic level by shear compliance measurements. The analysis reveals the strong coupling between the orientational processes of the chromophores and the polymer chain dynamics. The effects of other physical parameters (applied voltage magnitude, amount of plasticizer, average molecular weight of the polymer host) on the orientational dynamics of chromophores are also investigated in order to describe the mechanical interactions between the chromophores and the polymer host. Finally, a new way of optimization for photorefractive polymeric material properties is suggested.
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Jean-Charles Ribierre, Loiec Mager, Alain F. Fort, and Stephane Mery "Effects of the viscoelastic properties on the orientational dynamics of chromophores in low Tg guest-host polymers", Proc. SPIE 4798, Linear and Nonlinear Optics of Organic Materials II, (18 December 2002); https://doi.org/10.1117/12.452127
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