Dielectric relaxation studies on thermotropic side-chain liquid crystalline polymers

Garcı́a-Bernabé, Abel; Díaz‐Calleja, Ricardo

doi:10.1002/1097-0126(200101)50:1<165::aid-pi620>3.0.co;2-w

Cited by 6 publications

(2 citation statements)

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“…The temperature dependence of the characteristic peak frequency of γ -and β-relaxations exhibits a linear Arrhenius behavior while δand α-relaxations obey the Vogel-Fulcher-Tammann (VFT) relations [4,8,14,15,17]. Rarely, for δ-relaxation of a SCLCP linear Arrhenius evolutions are observed with temperature as reported in [19]. In a study of combined dielectric and viscosimetric measurements [20], Seiberle and co-workers reported the important role of the temperature dependent viscosity in the relaxation process.…”

Section: Introductionmentioning

confidence: 84%

“…For this purpose a dielectric spectroscopy of unaligned thermotropic side chain liquid crystalline polymer (TSCLCP) poly(6-(4-cyanobiphenyl-4 -oxy)hexyl acrylate) based on biphenylene mesogens spaced with six methylene groups (CBPA6) has been investigated in this work. Additionally, in the past, poly(3-(4-cyanobiphenyl-4 -oxy)propyl acrylate)-CBPA3-having three methylene groups as a flexible spacer has been investigated using the dielectric technique [19]. In that study, four distinct dielectric relaxations for CBPA3 were revealed and information on the order parameter was also obtained from the experimental data.…”

Section: Introductionmentioning

confidence: 99%

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Dielectric relaxation in a thermotropic side chain liquid crystalline polymer with nematic reentrant phase

Salehli

Yildiz

Özbek

et al. 2007

J. Phys.: Condens. Matter

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Dielectric spectroscopy of liquid crystalline cyanobiphenyl polyacrylates (CBPA6) with six methylene groups in the side chain has been investigated in the frequency range of 30 Hz–13 MHz and in the temperature interval from 100 to 470 K. From the temperature dependence of ε′(T), the anomalies corresponding to sequential phase transitions of liquid crystalline mesophases were revealed. The observed α- and δ-relaxation processes were described by the Vogel–Fulcher–Tammann law. It was found that δ-relaxation exhibits a multistage slowing behavior with decreasing temperature. The existence of a reentrant nematic (Nre) phase upper glassy phase shows us the special conditions for glass transition: the enhancement of the degree of cooperativity in mesogenic subsystems due to corrugation effects results in interaction of the side chain modes with a mixture of segmental and normal modes of the backbone, leading to a step-like anomaly of ε′(T) at the glass transition.

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