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Dynamics of 4-(2-hexyloxy-ethoxy) 4'-cyanobiphenyl Molecules on Approaching a Glass Transition as Studied by Dielectric Spectroscopy

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Massalska-Arodź M., Witko W., Gorbachev V., Hartmann L., Kremer F.

Acta Physica Polonica A

2003

vol. 104

issue 6

527-536

The complex dielectric permittivity of 4-(2-hexyloxy-ethyloxy) 4'-cyano-biphenyl measured in the frequency range from 0.03 Hz to 10^9 Hz is presented. Monotropic sequence of thermodynamic phases was found with two stable phases (isotropic and crystal) and three metastable states (supercooled isotropic phase, its glass and a smectic phase observed only on heating the sample first cooled rapidly to the liquid nitrogen temperature). In isotropic and supercooled isotropic phases the temperature dependence of the dielectric relaxation time was described by the same Vogel-Fulcher-Tammann formula while in a smectic phase it was of the Arrhenius type. In the transition from a supercooled isotropic phase to a smectic phase the relaxation rate of molecular motions around the short axes increases by two decades. Comparison of the relaxation behaviour and polymorphism of 4-(2-hexyloxy-ethyloxy) 4'-cyano-biphenyl of linear molecules with two chiral cyanobiphenyls is discussed.

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1 Acta Physica Polonica A

1 2003

1 Gorbachev V.

1 Hartmann L.

1 Kremer F.

1 Massalska-Arodź M.

1 Witko W.

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Dynamics of 4-(2-hexyloxy-ethoxy) 4'-cyanobiphenyl Molecules on Approaching a Glass Transition as Studied by Dielectric Spectroscopy