Eur. Phys. J. E 7, 387-392 (2002)
Glassy and fluidlike behavior of the isotropic phase of n-cyanobiphenyls in broad-band dielectric relaxation studiesS.J. Rzoska1, M. Paluch1, A. Drozd-Rzoska1, J. Ziolo1, P. Janik1 and K. Czuprynski2
1 Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland
2 Military Technical University, ul. S. Kaliskiego, Warsaw, Poland
(Received 22 November 2001)
It is shown that the temperature behavior of peaks of dielectric loss curves in the isotropic phase of n-cyanobiphenyls with isotropic-nematic and isotropic-smectic A transitions exhibits features characterisic for both supercooled, glass-forming liquids and critical, binary mixtures. The behavior of can be portrayed by the Vogel-Fulcher-Tamman relation and the "critical-like", mode-coupling theory (MCT) equation. The latter is supported by the novel analysis of electric conductivity . The obtained and dependencies can be related by using the fractional Debye-Einstein-Stokes law. For all tested mesogens the static dielectric permittivities and are described by dependencies resembling those applied in the homogeneous phase of critical mixtures but with specific-heat critical exponent . This behavior agrees with the novel fluidlike description for the isotropic-nematic transition (P.K. Mukherjee, Phys. Rev. E 51, 5745 (1995); A. Drozd-Rzoska, Phys. Rev. E 59, 5556 (1999)). The obtained glassy features of dielectric relaxation support the recent simulation analysis carried out by M. Letz et al. (Phys. Rev. E 62, 5173 (2000)).
64.70.Md - Transitions in liquid crystals.
64.70.Pf - Glass transitions.
64.60.Ht - Dynamic critical phenomena.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002