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  • Title: Glassy and fluidlike behavior of the isotropic phase of n-cyanobiphenyls in broad-band dielectric relaxation studies.
    Author: Rzoska SJ, Paluch M, Drozd-Rzoska A, Ziolo J, Janik P, Czupryński K.
    Journal: Eur Phys J E Soft Matter; 2002 Apr; 7(4):387-92. PubMed ID: 27638170.
    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)).
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