Author
Sylwester J. Rzoska
Other affiliations: University of Silesia in Katowice, Silesian University
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.
Papers published on a yearly basis
Papers
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TL;DR: In this article, the shape of the relaxation function (nonexponentiality) and the temperature dependence of relaxation times (e.g., fragility) were investigated for molecular glass-formers.
Abstract: There is a well-known correlation between the shape of the relaxation function (nonexponentiality) and the temperature-dependence of the relaxation times (e.g., fragility), with broader relaxations associated with steeper Tg-normalized temperature dependences. Herein, exceptions to this correlation are described. Five molecular glass-formers, all having very similar relaxation functions, are found to exhibit a range of fragilities. We also show for two of these materials that, while pressure does not affect the breadth of the relaxation function, it substantially reduces the fragility.
19 citations
TL;DR: In this paper, preliminary results of time-resolved nonlinear dielectric effect (NDE) studies in the liquid, glass-forming epoxy resin EPON 5 are presented.
Abstract: Preliminary results of time-resolved nonlinear dielectric effect (NDE) studies in the liquid, glassforming epoxy resin EPON 5 are presented. For all tested temperatures the NDE response of the sample parametrizes the stretched exponential function with exponent $\ensuremath{\beta}=0.38\ifmmode\pm\else\textpm\fi{}0.05.$ The temperature evolution of relaxation times can be parametrized by means of the Vogel-Fulcher-Tammann function ${\ensuremath{\tau}}^{\mathrm{NDE}}={\ensuremath{\tau}}_{0}^{\mathrm{NDE}}\mathrm{exp}{(D}_{\mathrm{NDE}}{T}_{0}^{\mathrm{NDE}}/T\ensuremath{-}{T}_{0}^{\mathrm{NDE}}),$ with ${\ensuremath{\tau}}_{0}^{\mathrm{NDE}}\ensuremath{\approx}0.3\mathrm{s},$ ${D}_{E}\ensuremath{\approx}1.2,$ and ${T}_{0}^{\mathrm{NDE}}\ensuremath{\approx}261\mathrm{K}.$ The latter value is, within the limit of the experimental error, equal to the glass temperature ${T}_{g}.$ The relaxation of ``nonlinear'' changes of the dielectric permittivity induced by a strong, steady electric field may be associated with the dynamic equilibrium of glassy clusters and the surrounding fluidlike region.
19 citations
TL;DR: It is suggested that for each nCB a unique, characteristic minimal value of ΔT, associated with the I-N-SmA triple point, exists and can be hidden in the negative pressures domain for 'shorter' nCBs, and the possibility of the extension of the 'melting curve' into thenegative pressures region as well as the appearance of the'melting inversion' at high enough pressures is indicated.
Abstract: Results of the extended Landau?de Gennes model analysis and experimental studies of the isotropic?nematic (I?N) and isotropic?smectic-A (I?SmA) phase transitions in rod-like liquid crystalline n-alkylcyanobiphenyls are presented. Experiments were carried out as a function of temperature and pressure using the static dielectric permittivity and its ?nonlinear? (strong electric field related) counterpart?the low-frequency nonlinear dielectric effect. Precise estimations of the values of the discontinuity of the isotropic?mesophase transitions (?T) for nCB from n?=?3?14 have been obtained. It is suggested that for each nCB a unique, characteristic minimal value of ?T, associated with the I?N?SmA triple point, exists. For ?shorter? nCBs it can be hidden in the negative pressures domain. The possibility of the extension of the ?melting curve? into the negative pressures region as well as the appearance of the ?melting inversion? at high enough pressures is indicated.
19 citations
TL;DR: Broadband dielectric spectroscopy is employed to investigate the non-Debye relaxation behavior in a dendrimeric alkyd resin, and from temperature-dependent measurements at ambient pressure, a very broad distribution of relaxation times is found.
Abstract: Broadband dielectric spectroscopy is employed to investigate the non-Debye relaxation behavior in a dendrimeric alkyd resin. From temperature-dependent measurements at ambient pressure, we found a very broad distribution of relaxation times. This is attributed to the complex geometrical topology of the molecule. However, compression significantly reduces the non-Debye character of the dielectric response; thus, pressure induces dynamic homogeneity in the dendrimeric alkyd resin.
18 citations
TL;DR: In this article, the authors investigated the exponent of the power law with a constant exponent based on an equation of state model and experimental data for various chain-molecule solutions and showed that the exponent depends on the chain length of the dissolved chain molecules.
Abstract: The dependence of the critical volume fraction at constant pressure as a function of the chain length of a polymer/solvent system can be described by a power law. The exponent of this power law is investigated based on an equation of state model and experimental data for various chain-molecule solutions here. The results are compared to recent molecular simulation data taken from the literature and analytical models. The theoretical models, simulation, and experimental data show that the exponent depends on the chain length of the dissolved chain molecules. The power law with a constant exponent is therefore not a universal relationship for this dependence. Based on the investigation of the chain length dependence a correlation for the critical volume fraction is proposed here. This function generalizes the Flory and a renormalization group model and is applied to the correlation of the experimental data. This more general relationship includes the power law with the exponent obtained from the Flory theory as limiting behavior. Some additional experimental data for oligomer solutions which are necessary for an investigation of the short chain length limit have been measured.
18 citations
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TL;DR: In this paper, the critical behavior of spin systems at equilibrium is studied in three and two dimensions, and the results in three-dimensional space are presented in particular for the six-loop perturbative series for the β -functions.
1,363 citations
TL;DR: This work identifies the class of secondary relaxations that bears a strong connection or correlation to the primary relaxation in all the dynamic properties and proposes that only these should be called the Johari-Goldstein beta-relaxation.
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; ...
715 citations
TL;DR: In this paper, a review of the mechanisms underlying the relaxation properties of glass-forming liquids and polymers is provided, with an emphasis in the insight provided into the mechanism underlying the glass relaxation properties.
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
638 citations
TL;DR: Although differential scanning calorimetry is the most widely used thermal analytical technique applied to the characterization of amorphous solid dispersions, there are many established and emerging techniques which have been shown to provide useful information.
399 citations
345 citations