Dielectric relaxation phenomena in side-chain liquid-crystalline polycarbosilane of various spacer lengths

Maria Mucha; Joseph Grzyb; Andreas Schoenhals

doi:10.1117/12.373705

14 December 1999 Dielectric relaxation phenomena in side-chain liquid-crystalline polycarbosilane of various spacer lengths

Maria Mucha, Joseph Grzyb, Andreas Schoenhals

Author Affiliations +

Proceedings Volume 4017, Polymers and Liquid Crystals; (1999) https://doi.org/10.1117/12.373705
Event: International Conference on Dielectric and Related Phenomena '98, 1998, Szczyrk, Poland

Abstract

Dielectric loss has been measured over the frequency 10^-2-10⁶ Hz between -100 degrees C to 80 degrees C for side-chain liquid crystalline carbosilanes, whose different mesophase structure was reached by the variation of the number of alkyl spacer groups. Three relaxation processes known as (beta) , (alpha) and (delta) were found and discussed. The characteristic (beta) relaxation corresponds to fluctuational dynamics of a transverse component of dipole moment which has Arrhenius-like character. Its activation energy E_a(beta ) changes with an increasing spacer length. The non Arrhenius-like (alpha) process is related to a dynamic glass transition of the polycarbosilanes. The (delta) process connected with rotational fluctuation of mesogenic longitudinal dipoles around short axis is observed over the whole range of frequency. The activation energy E_a(delta ) of (delta) relaxation depends on the polymer order and the phase structure such as: glassy amorphous, viscoelastic amorphous, mesomorphic or isotropic reached at various temperatures. E_a(delta ) value ranges from 32 kJ/mol to 120 kJ/mol. Electro-optical effect for the sample with x equals 4 is observed at various temperatures with varying intensity. In the vicinity of isotropization the reorientational effect due to electric field is suppressed by heat disorder.

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Maria Mucha, Joseph Grzyb, and Andreas Schoenhals "Dielectric relaxation phenomena in side-chain liquid-crystalline polycarbosilane of various spacer lengths", Proc. SPIE 4017, Polymers and Liquid Crystals, (14 December 1999); https://doi.org/10.1117/12.373705

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