Abstract
Recently, the isotropic phase of rod-like liquid crystalline compounds is advised as an experimental model system for studying complex glassy dynamics. One of unique phenomena occuring close to the glass temperature, for the time scale 10−7±1 s <τ < τ (T g ) ≈ 100s, is the fractional Debye-Stokes-Einstein (FDSE) behaviour στ = const with S<1, i.e. the coupling of dc conductivity (σ, translational processes) and dielectric (structural) relaxation time (τ, orientational processes). It is shown that this relation may be found also in the isotropic phase of nematic liquid crystalline compounds n-pentylcyanobiphenyl (5CB), although surprisingly for time-scales τ<10−8 s. The application of the derivative based analysis revealed a change of S on cooling towards the isotropic — nematic transition. The optimal description of the evolution of relaxation time and conductivity by the mode-coupling theory (MCT) dependence in the isotropic phase is shown: τ(t) ∞ (T−T Mct ) and σ (T) ∞ (T-T MCT ), where T MCT ≈T I−N −33K and T > T I−N is shown. The link between this behavior and the FDSE is suggested, namely: S = ϕ′/ϕ. Finally the call for further pressure studies is formulated.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Donth, E. (2001) The Glass Transition: Relaxation Dynamics in Liquids and Disordered Materials (Springer Verlag, Berlin)
Kremer, F., and Shoenhals, A. (eds.) (2003) Broad Band Dielectric Spectroscopy (Springer, Berlin)
Rzoska, S. J., and Mazur, V. (eds.) (2006) Soft Matter Under Exogenic Impacts, NATO Sci. Series II, (Springer, Berlin), vol. 24
Kivelson, S. A., and Tarjus, G. (2008) In search of a theory of supercooled liquids, Nature Materials 7, 831–833
McKenna, G. B. (2008) Diverging views on glass transition, Nature Physics 4, 673–674
Hecksher, T., Nielsen, A. I., Olsen, N. B., and Dyre, J. C. (2008) Little evidence for dynamic divergences in ultraviscous molecular liquids, Nature Physics 4, 737–741
Douglas, J. F., Leporini, D. (1998) Obstruction model of the fractional Stokes-Einstein relation in glass-forming liquids, J. Non-Cryst. Solids 23–237, 137–141
Corezzi, S., Lucchesi, M., Rolla P. A., Capaccioli, S., Gallone, G. (1999) Temperature and pressure dependences of the relaxation dynamics of supercooled systems explored by dielectric spectroscopy, Phil. Mag. B 79, 1953–1963
Hensel Bielowka, S., Psurek, T., Ziolo, J., and Paluch, M. (2001) Test of the fractional Debye-Stokes-Einstein equation in low-molecular-weight glass-forming liquids under condition of high compression, Phys. Rev. E 63, 062301
Wang, C. H. (2002) Enhancement of translational diffusion coefficient of a probe in a rotationally anisotropic fluid, Phys. Rev. E 66, 021201
Funke, K., Banhatti, R. D., Brueckner, S., Cramer, C., and Wilmer, D. (2002) Dynamics of mobile ions in crystals, glasses and melts, described by the concept of mismatch and relaxation, Solid State Ionics 154–155, 65–74
Cutroni, M., Mandanici, A., and De Francesco, L. (2002) Fragility, stretching parameters and decoupling effect on some supercooled liquids, J. Non-Cryst. Solids 307–310, 449–454
Power, G., Johari, P., and Vij, J. K. (2002) Effects of ions on the dielectric permittivity and relaxation rate and the decoupling of ionic diffusion from dielectric relaxation in supercooled liquid and glassy 1-propanol, J. Chem. Phys. 116, 419–4201
Bordat, P., Affouard, F., Descamps, M., and Mueller-Plathe, F. (2003) The breakdown of the Stokes—Einstein relation in supercooled binary liquids, J. Phys.: Condens. Matt. 15, 5397–5407
Psurek, T., Ziolo, J., and Paluch, M. (2004) Analysis of decoupling of DC conductivity and structural relaxation time in epoxies with different molecular topology, Physica A 331, 353–364
Richert, R. (2005) Dielectric responses in disordered systems: From molecules to materials, J. Non-Cryst. Solids 351, 2716–2722
Becker, S. R., Poole, P. H., and Starr, F. W. (2006) Fractional Stokes-Einstein and Debye-Stokes-Einstein Relations in a Network-Forming Liquid, Phys. Rev. Lett. 97, 055901
Drozd-Rzoska, A., and Rzoska, S. J. (2006) Derivative-based analysis for temperature and pressure evolution of dielectric relaxation times in vitrifying liquids, Phys. Rev. E 73, 041502
Drozd-Rzoska, A., Rzoska. S. J., Roland, C. M., and Imre, A. R. (2008) On the pressure evolution of dynamic properties of supercooled liquids J. Phys.: Condens. Matt. 20, 244103
Novikov, V. N., and Sokolov, A. P. (2003) Universality of the dynamic crossover in glass-forming liquids: a “magic” relaxation time, Phys. Rev. E 67, 031507
Demus, D., Goodby, J., Gray, G. W., Spiess, H. W., and Vill, V. (eds.) (1998) Handbook of Liquid Crystals, edited by vol. 1: Fundamentals (Springer, Berlin)
Drozd-Rzoska, A., Rzoska, S. J., and Czupryński, K. (2000) Phase transitions from the isotropic liquid to liquid crystalline mesophases studied by “linear” and “nonlinear” static dielectric permittivity, Phys. Rev. E 61, 5355–5360
Rzoska, S. J., Paluch, M., Drozd-Rzoska, A., Paluch, M., Janik, P., Zioło J., and Czupryński, K. (2001) Glassy and fluidlike behavior of the isotropic phase of mesogens in broad-band dielectric, Europ. Phys. J. E 7, 387
Rzoska, S. J., and Drozd-Rzoska, A. (2002) On the tricritical point of the isotropic — nematic transition in a rod-like mesogen hidden in the negative pressure region, in NATO Sci. Series II, vol. 84, Liquids under negative pressures, eds.: Imre, A. R., Maris, H. J., and Williams P. R. (Kluwer-Springer, Dordrecht) p. 116
Drozd-Rzoska, A. (2006) Heterogeneity-related dynamics in isotropic n-pentylcyanobiphenyl, Phys. Rev. E 73, 022501
Drozd-Rzoska, A. (2009) Glassy dynamics of liquid crystalline 4'-n-pentyl-4-cyanobiphenyl (5CB) in the isotropic and supercooled nematic phase, J. Chem. Phys. 130, 234910
Cang, H., Li, J., Novikov, V. N., and Fayer, M. D. (2003) J. Chem. Phys. 119, 10421
Anisimov, M. A. Critical Phenomena in Liquids and in Liquid Crystals (1992) (Gordon and Breach, Reading)
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2010 Springer Science+Business Media B.V.
About this paper
Cite this paper
Drozd-Rzoska, A., Rzoska, S.J. (2010). Anomalous Decoupling of the dc Conductivity and the Structural Relaxation Time in the Isotropic Phase of a Rod-Like Liquid Crystalline Compound. In: Rzoska, S., Drozd-Rzoska, A., Mazur, V. (eds) Metastable Systems under Pressure. NATO Science for Peace and Security Series A: Chemistry and Biology. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-3408-3_10
Download citation
DOI: https://doi.org/10.1007/978-90-481-3408-3_10
Publisher Name: Springer, Dordrecht
Print ISBN: 978-90-481-3406-9
Online ISBN: 978-90-481-3408-3
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)