Jan Jadżyn

Bio: Jan Jadżyn is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Liquid crystal & Dielectric. The author has an hindex of 25, co-authored 234 publications receiving 2453 citations. Previous affiliations of Jan Jadżyn include Katholieke Universiteit Leuven.

Viscous Behavior of Binary Mixtures of Mesogenic Solvent/Non-Mesogenic Solute

Abstract: The paper presents results of the shear viscosity measurements performed on diluted binary mixtures of mesogenic solvent n-hexylcyanobiphenyl (C6H13PhPhC≡N, 6CB) and two non-mesogenic admixtures: (i) n-heptylcyanophenyl (C7H15PhC≡N, 7CP), composed of the molecules of the same polarity as the solvent molecules but of a slightly shorter length, and (ii) 4-n-propylcyclohexyl-4’-n-pentylphenyl (C3H7CyHxPhC5H11, 3CyP5), composed of the non-polar molecules but of a length very close to that of the mesomorphic solvent molecules. The experiment showed that the concentrational depression of the clearing temperature and the temperature extent of the isotropic + nematic (I + N) two-phase region in the mixtures are significantly smaller, i.e. the nematic phase is more thermodynamically stable, when the admixture molecular length is compatible to that of the mesogenic solvent, regardless of the polarity of the admixture molecules. The activation energy for freely flowing mixtures in the isotropic, nematic, and two-phase I + N regions was determined and discussed.

Shear Viscosity of Mixtures of α-Tocopherol with Nonpolar Solvents†

Abstract: Shear viscosities (η) of the binary mixtures of α-tocopherol (vitamin E) with 4-n-propylcyclohexyl-4′-n-pentylphenyl and mesitilene, two nonpolar solvents composed of the molecules of essentially different shape, have been measured in the temperature range from (278 to 353) K. In the whole concentration range of α-tocopherol in both solvents, the dependence of η on T can be well described by the Vogel−Fulcher−Tammann equation. The viscosity deviations from the additive behavior are strongly negative, and their concentration dependence was fitted to the Redlich−Kister equation.

Shear Viscosity of the Homologous Series of wCHBT (n = 0 ÷ f 12) in the Isotropic and Nematic Phases

Abstract: Abstract The paper presents results of shear viscosity measurements performed on nematogenic 4-(trans-4'-n-alkylcyclohexyl)isothiocyanatobenzenes (CnH 2n + 1-CyHx-Ph-N=C=S, /nCHBT) in the isotropic (n = 0 ÷ 12) and nematic (« = 4 ÷ 12) phases. The viscosity measured in the nematic phase is, due to the flow alignment phenomenon, close to the Migsowicz T? 2 viscosity coefficient. An odd-even effect in the n dependence of the viscosity-activation energy is observed both in the nematic and isotropic phases of nCHBT.

The structural transitions in a nematic liquid crystals doped with magneticaly labeled carbon nanotubes

Abstract: Z. Mitróová, N. Tomašovičová, M. Koneracká, V. Závǐsová, M. Timko, J. Kováč, P. Kopčanský, L. Tomčo, N. Éber, K. Fodor-Csorba, T. Tóth-Katona, A. Vajda, J. Jadzyn, E. Beaugnon, X. Chaud 1 Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia 2 Faculty of Aeronautics, Technical University, Rampova 7, 041 21 Košice, Slovakia 3 Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary 4 Institute of Molecular Physics, Polish Academy of Sciences, Smoluchovskiego 17, 60179 Poznan, Poland 5 Grenoble High Magnetic Field Laboratory, Centre National de la Recherche Scientifique, 25 Avenue des Martyrs, Grenoble, France

From supramolecular to conventional polymers: polyethylene glycol

Abstract: Increasing the polymerization degree of polyethylene glycol (PEG), HO–(CH2CH2O–)nH, entails lowering the number of hydroxyl groups per unit volume; therefore, supramolecular polymers are gradually replaced by longer and longer conventional polymers. This paper concerns an estimation of the polymerization degree (n) where PEG changes its nature from a supramolecular polymer to a conventional polymer. It was found that that virtual transformation takes place when n reaches the value of about 9. The conclusion follows from the different thermal behaviors of the dipolar orientational effects in liquid PEG detected for n below and above 9. The result reflects a diametrically different impact of the temperature on the linkages between the monomers in supramolecular and conventional polymers.

The restaurant at the end of the random walk: recent developments in the description of anomalous transport by fractional dynamics

Abstract: Fractional dynamics has experienced a firm upswing during the past few years, having been forged into a mature framework in the theory of stochastic processes. A large number of research papers developing fractional dynamics further, or applying it to various systems have appeared since our first review article on the fractional Fokker–Planck equation (Metzler R and Klafter J 2000a, Phys. Rep. 339 1–77). It therefore appears timely to put these new works in a cohesive perspective. In this review we cover both the theoretical modelling of sub- and superdiffusive processes, placing emphasis on superdiffusion, and the discussion of applications such as the correct formulation of boundary value problems to obtain the first passage time density function. We also discuss extensively the occurrence of anomalous dynamics in various fields ranging from nanoscale over biological to geophysical and environmental systems.

A Medicinal Chemist’s Guide to Molecular Interactions

Abstract: Molecular recognition in biological systems relies on the existence of specific attractive interactions between two partner molecules. Structure-based drug design seeks to identify and optimize such interactions between ligands and their host molecules, typically proteins, given their three-dimensional structures. This optimization process requires knowledge about interaction geometries and approximate affinity contributions of attractive interactions that can be gleaned from crystal structure and associated affinity data. Here we compile and review the literature on molecular interactions as it pertains to medicinal chemistry through a combination of careful statistical analysis of the large body of publicly available X-ray structure data and experimental and theoretical studies of specific model systems. We attempt to extract key messages of practical value and complement references with our own searches of the CSDa,(1) and PDB databases.(2) The focus is on direct contacts between ligand and protein functional groups, and we restrict ourselves to those interactions that are most frequent in medicinal chemistry applications. Examples from supramolecular chemistry and quantum mechanical or molecular mechanics calculations are cited where they illustrate a specific point. The application of automated design processes is not covered nor is design of physicochemical properties of molecules such as permeability or solubility. Throughout this article, we wish to raise the readers’ awareness that formulating rules for molecular interactions is only possible within certain boundaries. The combination of 3D structure analysis with binding free energies does not yield a complete understanding of the energetic contributions of individual interactions. The reasons for this are widely known but not always fully appreciated. While it would be desirable to associate observed interactions with energy terms, we have to accept that molecular interactions behave in a highly nonadditive fashion.3,4 The same interaction may be worth different amounts of free energy in different contexts, and it is very hard to find an objective frame of reference for an interaction, since any change of a molecular structure will have multiple effects. One can easily fall victim to confirmation bias, focusing on what one has observed before and building causal relationships on too few observations. In reality, the multiplicity of interactions present in a single protein−ligand complex is a compromise of attractive and repulsive interactions that is almost impossible to deconvolute. By focusing on observed interactions, one neglects a large part of the thermodynamic cycle represented by a binding free energy: solvation processes, long-range interactions, conformational changes. Also, crystal structure coordinates give misleadingly static views of interactions. In reality a macromolecular complex is not characterized by a single structure but by an ensemble of structures. Changes in the degrees of freedom of both partners during the binding event have a large impact on binding free energy. The text is organized in the following way. The first section treats general aspects of molecular design: enthalpic and entropic components of binding free energy, flexibility, solvation, and the treatment of individual water molecules, as well as repulsive interactions. The second half of the article is devoted to specific types of interactions, beginning with hydrogen bonds, moving on to weaker polar interactions, and ending with lipophilic interactions between aliphatic and aromatic systems. We show many examples of structure−activity relationships; these are meant as helpful illustrations but individually can never confirm a rule.

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

Ionic Liquid Crystals: Versatile Materials.

Abstract: This Review covers the recent developments (2005-2015) in the design, synthesis, characterization, and application of thermotropic ionic liquid crystals. It was designed to give a comprehensive overview of the "state-of-the-art" in the field. The discussion is focused on low molar mass and dendrimeric thermotropic ionic mesogens, as well as selected metal-containing compounds (metallomesogens), but some references to polymeric and/or lyotropic ionic liquid crystals and particularly to ionic liquids will also be provided. Although zwitterionic and mesoionic mesogens are also treated to some extent, emphasis will be directed toward liquid-crystalline materials consisting of organic cations and organic/inorganic anions that are not covalently bound but interact via electrostatic and other noncovalent interactions.