Broadband dielectric spectroscopy on side group liquid crystal polymers

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Abstract
Dielectric studies on three liquid-crystalline side group polymers were performed in the temperature range from 100 K to 450 K and in the frequency range from 10−1 Hz to 107 Hz. All samples exhibit an α relaxation with a WLF dependence of the activation energy as well as a β relaxation, which are comparable in the glassy state. Their mean relaxation times, their relaxation time distribution, in its asymmetry and half-width, and their activation energies are nearly unaffected by the spacer length, terminal group and/or main chain. These findings are supported by N.M.R. measurements. A third relaxation process occurring close to the clearing point is also observed and assigned to the cooperative rotation of the side group around the main chain.

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