Dielectric relaxation and molecular dynamics of liquid crystalline side-chain oligoacrylates with 4-cyanazobensene side mesogenic groups in external electric or mechanical fields

N. A. Nikonorova; T. I. Borisova; A. I. Stakhanov; Valery P. Shibaev

doi:10.1117/12.301301

1 January 1998 Dielectric relaxation and molecular dynamics of liquid crystalline side-chain oligoacrylates with 4-cyanazobensene side mesogenic groups in external electric or mechanical fields

N. A. Nikonorova, T. I. Borisova, A. I. Stakhanov, Valery P. Shibaev

Author Affiliations +

Proceedings Volume 3319, Liquid Crystals: Chemistry and Structure; (1998) https://doi.org/10.1117/12.301301
Event: Liquid Crystals, 1997, Zakopane, Poland

Abstract

Dielectric relaxation and molecular mobility have ben investigated over the frequency range 60Hz-1MHz between 160 degrees C and 150 degrees C for smectic side-chain oligoacrylates with 4-cyanazobenzene mesogenic side groups and methylene spacers of different length. The studied oligomers were oriented by electric or mechanic fields. In the range of subglass temperatures two dielectric processes were observed - the (gamma) ₁ and the (beta) . The (gamma) ₁ process reflects the local motion of the spacer groups and the (beta) process is connected with the local motion of the mesogenic moieties. the molecular mobility of the (gamma) ₁ process increases with the spacer lengthening but at the same time in the case of the (beta) process the mobility is not changed. In LC state near T_g transition, the temperature-frequency dependencies of dielectric losses show two cooperative processes, the (alpha) - an the (delta) , related to the reorientation of the transverse or longitudinal components of the dipole moment of the mesogenic group, correspondingly. The preliminary orientation in external electric or mechanic fields leads to the establishment of planar or homeotropic orientation of the side mesogenic groups. The order parameters of oriented films were calculated. It was shown the planar or homeotropic orientation of mesogenic groups did not influence on relaxation times of the observed dielectric processes.

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N. A. Nikonorova, T. I. Borisova, A. I. Stakhanov, and Valery P. Shibaev "Dielectric relaxation and molecular dynamics of liquid crystalline side-chain oligoacrylates with 4-cyanazobensene side mesogenic groups in external electric or mechanical fields", Proc. SPIE 3319, Liquid Crystals: Chemistry and Structure, (1 January 1998); https://doi.org/10.1117/12.301301

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