Search results for "Surface Chemistry"

Kommentar zu der Arbeit von Hans Craubner: „Lösefraktionierapparatur für makromolekulare Stoffe”

1976

Cyclopolymerisation bei zweifach-ungesättigten Monomeren

1967

Das Prinzip der Cyclopolymerisation wird erlautert; an Beispielen wird gezeigt, welche Verbindungen zu intra-intermolekularen Wachstumsschritten befahigt sind. Der Gehalt an cyclischen Grundbausteinen in den gebildeten Polymerisaten hangt auser von der Struktur der Monomeren auch von den Polymerisationsbedingungen ab. Es werden stereochemische Fragen behandelt, die im Zusammenhang mit Ringschlusreaktionen an 6- und hohergliedrigen Ringen auftreten. Chemische Umsetzungen an Cyclopolymeren konnen zu Copolymeren mit bestimmter Zusammensetzung und regelmasigem Aufbau fuhren.

Light Induced Excited Pair Spin State in an Iron(II) Binuclear Spin-Crossover Compound

1999

Light scattering - diagnostic methods for colloidal dispersions

1993

Abstract The increasing demand from the colloid research community for quick and noninvasive experimental techniques as well as the rapid progress of modern optics and electronics have led to a considerable expansion in the field of light scattering. This review introduces the basic concepts with some emphasis on novel approaches like the study of interacting particle systems, multiple scattering techniques, and non ergodic samples. Particular attention is then devoted to recent experimental progress towards more compact and rugged instruments.

Challenging the Prediction of Anionogenic Ferromagnetism for Rb4O6

2007

It has been suggested that Rb4O6 should be a half-metallic ferromagnet with the magnetic moment carried by the hyperoxide anions and a Curie temperature above room temperature. In the present work,...

Theoretical modeling of Langmuir monolayers

1999

Abstract We study coarse-grained continuum models for Langmuir monolayers by self-consistent field theory and by Monte Carlo simulations. Amphiphilic molecules are represented by stiff chains of monomers with one end grafted to a planar surface. In particular, we discuss the origin of successive fluid–fluid transitions, the possible origin of tilt order and the factors which determine the direction of tilt.

How do droplets on a surface depend on the system size?

2002

Abstract We investigate the thermodynamics of inhomogeneous polymer melts in the framework of a coarse grained off-lattice model. Properties of the liquid–vapour interface and the packing of the melt in contact with an attractive wall are considered. We employ Monte Carlo simulations in the grand canonical ensemble to determine excess free energies, the wetting temperature and the pre-wetting line, as well as the pre-wetting critical point. Having determined the wetting properties and the phase diagram of the model polymer, we perform canonical Monte Carlo simulations of small droplets on a surface. This allows us to study the dependence of droplet size on the wetting properties. It is foun…

Experimental determination of effective charges in aqueous suspensions of colloidal spheres

2003

Abstract We determined the low frequency conductivity σ , the phase behaviour and the shear modulus G of colloidal fluids, respectively solids prepared from deionised aqueous suspensions of highly charged spherical particles. Conductivity measures the number of freely moving small ions Z * σ and thus relates to the ion condensation process in the electric double layer under conditions of finite macro-ion concentrations. Phase behaviour and elasticity data are consistently described by a Debye–Huckel pair potential assuming pair-wise additive macro-ion interactions. Like Z * σ , also the effective charges Z * G derived from the elasticity data scales with the ratio of macro-ion radius to Bje…

Phonon Scattering through a Local Anisotropic Structural Disorder in the Thermoelectric Solid Solution Cu_2Zn_(1−x)Fe_xGeSe_4

2013

Inspired by the promising thermoelectric properties of chalcopyrite-like quaternary chalcogenides, here we describe the synthesis and characterization of the solid solution Cu(2)Zn(1-x)Fe(x)GeSe(4). Upon substitution of Zn with the isoelectronic Fe, no charge carriers are introduced in these intrinsic semiconductors. However, a change in lattice parameters, expressed in an elongation of the c/a lattice parameter ratio with minimal change in unit cell volume, reveals the existence of a three-stage cation restructuring process of Cu, Zn, and Fe. The resulting local anisotropic structural disorder leads to phonon scattering not normally observed, resulting in an effective approach to reduce th…

Self-assembly in surfactant-based liquid mixtures: Octanoic acid/Bis(2-ethylhexyl)amine systems

2012

Abstract The physico-chemical properties of Bis(2-ethylhexyl)amine (BEEA) plus octanoic acid (OA) mixtures have been investigated by IR, SAXS, WAXS, viscosimetry, and AC complex impedance spectroscopy in the whole composition range. Mainly driven by proton transfer from the acidic OA to the basic BEEA, the formation of stoichiometrically well-defined adducts takes place in the mixtures. This causes the slowing down of molecular dynamics and the increase in charge carrier number density. Interestingly, while the pure components possess no significant conductivity (about 10−12 S cm−1 at 25 °C), their mixtures show a composition-dependent enhanced conductivity (up to about 10−5 S cm−1), i.e., …