title: Glassy and fluidlike behavior of the isotropic phase of n-cyanobiphenyls in broad-band dielectric relaxation studies.
abstract: It is shown that the temperature behavior of peaks f p, of dielectric loss curves in the isotropic phase of n-cyanobiphenyls n = 8, 9, 10 with isotropic-nematic and isotropic-smectic A transitions exhibits features characterisic for both supercooled, glass-forming liquids and critical, binary mixtures. The behavior of f p T 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 σ T . The obtained f p T and σT dependencies can be related by using the fractional Debye-Einstein-Stokes law. For all tested mesogens the static dielectric permittivities ɛ(') T and T are described by dependencies resembling those applied in the homogeneous phase of critical mixturesbut with specific-heat critical exponent α≈ 0.5. 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)).
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice, Poland, Poland.
authors.forename: S J
authors.initials: SJ
authors.lastname: Rzoska
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice, Poland, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Paluch
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice, Poland, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Drozd-Rzoska
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice, Poland, Poland.
authors.forename: J
authors.initials: J
authors.lastname: Ziolo
authors.affiliation: Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice, Poland, Poland.
authors.forename: P
authors.initials: P
authors.lastname: Janik
authors.affiliation: Military Technical University, ul. S. Kaliskiego, Warsaw, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Czupryński
keywords: PACS. 64.70.Md Transitions in liquid crystals – 64.70.Pf Glass transitions – 64.60.Ht Dynamic critical phenomena