Sylwester J. Rzoska

Bio: Sylwester J. Rzoska is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Dielectric & Liquid crystal. The author has an hindex of 33, co-authored 216 publications receiving 3570 citations. Previous affiliations of Sylwester J. Rzoska include University of Silesia in Katowice & Silesian University.

Non-linear dielectric effect in the isotropic phase above the isotropic-cholesteric phase transition

Abstract: Using the Landau-de Gennes theory, the temperature, pressure and frequency dependence of the non-linear effect in the isotropic phase above the isotropic–cholesteric phase transition is calculated. The influence of pressure on the isotropic–cholesteric phase transition is discussed by varying the coupling between the orientational order parameter and the macroscopic polarization of polar cholesterics. Comparing the results of the calculations with existing data, we finally conclude that the model provides a description of the isotropic–cholesteric transition that takes all experimentally known features of the unusual negative and positive pretransitional effect in the isotropic phase of the system into account in a qualitatively correct way.

The Nonlinear Dielectric Effect in the Isotropic Phase of Nematogens

Abstract: Results are presented of studies of the nonlinear dielectric effect (NDE) for two frequencies (300 kHz and 61 MHz) of the weak measuring field in the isotropic phase of 4 heptyl 4′ cyanobiphenyl (7CB) For the smaller frequency the NDE increases markedly towards positive values on approaching the clearing point. For the higher frequency the increase is negative Despite this difference both pretransitional effects exhibit similar, mean - field temperature character. The observed behaviour coincide with relations between the relaxation time of prenematic fluctuation and measurement frequencies.

Critical behavior of dielectric permittivity and nonlinear dielectric effect in the isotropic phase of nematogens

Abstract: The paper shows that the behaviour of dielectric permittivity (e) and its changes in a strong electric field (nonlinear dielectric effect NDE) can be described in the way analogous to that applied in critical binaiy solutions. Basing onmeasurement in 4,4n4iexylcyanobiphenyl (6CB) and 4,4n4etracyanobipheny1 (4CB) it was possible to portray thetemperature behavior of s and NDE from T up to T + 50 K. In the case of 4CB the satisfied description was possible despite the fact that the sample erystallises before reaching the clearing point. NDE tests was conducted for the measurement frequencyf= 70 kHz, what allowed to avoid the influence of relaxation processes on results.Keywords: Isotropicnematic transition, critical phenomena, dielectric pernnttivity, nonlinear dielectric effect. 1. INTRODUCTION Experimental studies of nonlinear dielectric effect (NDE) in liquid dielectrics determine changes of dielectric pernlittivity induced by a strong electric AE E '; E E2 (I)where I and care dielectric permittivitites in a strong and weak electric field E, respectively.Yet first experimental studies in the isotropic phase in MBBA2 in 1978 showed that NDE exhibits near the isotropicnematic (FN) phase transition the same type of the pretransitional behavior as the Kerr effect (ICE) ,

Critical Behavior of the Dielectric Modulus in Nitrobenzene-Dodecane Mixture

Abstract: The dielectric properties of a homogenous critical mixture of nitrobenzene-decane were studied in the range 1 Hz< f 1 Mz. The temperature dependences of the “static” dielectric permittivity e � (1 MHz) and the electric conductivity σ (1 Hz) exhibit pretransitional anomalies which may be associated with the same critical exponent φ = 1 − α ≈ 0.88, where α is the critical exponent of the specific heat. The same data were analyzed using the dielectric modulus representation. They show loss curves for the imaginary part of the modulus M �� ( f ). It was found that the temperature evolutions of the peak frequency τ = 1/2π fp and the peak maximum of M �� = M �� ( f p) also exhibit critical anomalies. Their forms resemble anomalies obtained for the imaginary part of the dielectric permittivity e �� ( f), carried out for 40 MHz < f <1 GHz, in an ethanol-dodecane critical mixture [S. J. Rzoska, K. Orzechowski, and A. Drozd-Rzoska, Phys. Rev. E 65, 042501 (2002)]. – PACS: 64.70.Ja, 77.20.+y , 64.60.Fr

Classification of secondary relaxation in glass-formers based on dynamic properties.

Abstract: Dynamic properties, derived from dielectric relaxation spectra of glass-formers at variable temperature and pressure, are used to characterize and classify any resolved or unresolved secondary relaxation based on their different behaviors. The dynamic properties of the secondary relaxation used include: (1) the pressure and temperature dependences; (2) the separation between its relaxation time τβ and the primary relaxation time τα at any chosen τα; (3) whether τβ is approximately equal to the independent (primitive) relaxation time τ0 of the coupling model; (4) whether both τβ and τ0 have the same pressure and temperature dependences; (5) whether it is responsible for the “excess wing” of the primary relaxation observed in some glass-formers; (6) how the excess wing changes on aging, blending with another miscible glass-former, or increasing the molecular weight of the glass-former; (7) the change of temperature dependence of its dielectric strength Δeβ and τβ across the glass transition temperature Tg; ...

Supercooled dynamics of glass-forming liquids and polymers under hydrostatic pressure

Abstract: An intriguing problem in condensed matter physics is understanding the glass transition, in particular the dynamics in the equilibrium liquid close to vitrification Recent advances have been made by using hydrostatic pressure as an experimental variable These results are reviewed, with an emphasis in the insight provided into the mechanisms underlying the relaxation properties of glass-forming liquids and polymers