A5037945714- Material Dynamics and Properties
- Rheology and Fluid Dynamics Studies
- NMR spectroscopy and applications
- Polymer crystallization and properties
- Nuclear Physics and Applications
- Surfactants and Colloidal Systems
- Polymer Nanocomposites and Properties
- Advanced Polymer Synthesis and Characterization
- Quantum, superfluid, helium dynamics
- Advanced NMR Techniques and Applications
- Muon and positron interactions and applications
- Spectroscopy and Quantum Chemical Studies
- Block Copolymer Self-Assembly
- Theoretical and Computational Physics
- Force Microscopy Techniques and Applications
- Hydrogen Storage and Materials
- Particle accelerators and beam dynamics
- Advanced Physical and Chemical Molecular Interactions
- Particle Accelerators and Free-Electron Lasers
- Protein Structure and Dynamics
- Electrostatics and Colloid Interactions
- Phase Equilibria and Thermodynamics
- High-pressure geophysics and materials
- Atomic and Subatomic Physics Research
- Lipid Membrane Structure and Behavior
Forschungszentrum Jülich
2016-2025
China Spallation Neutron Source
2025
Institut Laue-Langevin
1989-2021
Heinz Maier-Leibnitz Zentrum
2010-2021
Helmholtz-Zentrum Berlin für Materialien und Energie
2010-2020
Stadtwerke Jülich (Germany)
1991-2019
The University of Texas at Austin
2017-2019
Pohang University of Science and Technology
2015-2019
Institute for Complex Systems
2011-2019
Deutsche Nationalbibliothek
2019
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConnection between Polymer Molecular Weight, Density, Chain Dimensions, and Melt Viscoelastic PropertiesL. J. Fetters, D. Lohse, Richter, T. A. Witten, ZirkelCite this: Macromolecules 1994, 27, 17, 4639–4647Publication Date (Print):August 1, 1994Publication History Published online1 May 2002Published inissue 1 August 1994https://pubs.acs.org/doi/10.1021/ma00095a001https://doi.org/10.1021/ma00095a001research-articleACS PublicationsRequest reuse...
Combining statistical-mechanical theories and neutron-scattering techniques, we show that the effective pair potential between star polymers is exponentially decaying for large distances crosses over, at a density-dependent corona diameter, to an ultrasoft logarithmic repulsion small distances. We also make theoretical prediction in concentrated polymer solutions, this interaction induces anomalous fluid structure factor which exhibits unusually pronounced second peak.
Recent neutron scattering experiments on the microscopic dynamics of polymers below and above glass transition temperature T(g) are reviewed. The results presented cover different dynamic processes appearing in glasses: local motions, vibrations, relaxation such as alpha- beta-relaxation. For alpha-relaxation, which occurs T(g), it is possible to extend time-temperature superposition principle, valid for a macroscopic scale, time scale. However, this principle not applicable temperatures...
The local dynamics of 1,4 polybutadiene below and above the merging \ensuremath{\alpha} \ensuremath{\beta} relaxations have been investigated by combining neutron spin echo (NSE) dielectric spectroscopy. study dynamic structure factor measured NSE over a wide momentum transfer range allows us to characterize relaxation as an interchain process while originates from mainly intrachain motions. At temperatures merging, can be described superposition elemental processes for obtained motions...
We present neutron-spin-echo data on the structural relaxation of glass-forming polybutadiene near glass transition. Microscopic dynamics scale an interchain distance and monomeric friction coefficient derived from macroscopic viscosity obey time-temperature superposition principle following a common scale. The dynamic structure factor exhibits strong similarities with recent mode-coupling predictions.
Neutron time-of-flight data of polybutadiene and polyisoprene in a wide temperature range around the glass transition are reported. The anharmonic part spectra is evaluated using recently developed time domain Fourier transform technique. results corroborate recent finding two different domains dynamics, one above crossover about 2 ps other below it. Two interpretations short behavior considered, namely fast Debye regime \ensuremath{\alpha} relaxation vibrational softening boson peak.
Using neutron-spin-echo and time-of-flight spectroscopy we have investigated the precise temperature dependence of elastic (nonergodic) fraction in spectrum density fluctuations glass-forming polymer polybutadiene. With increasing found a critical decrease normalized intensity following closely (${\mathit{T}}_{\mathit{c}}$-T${)}^{1/2}$ behavior predicted by mode-coupling theory. The was determined to be ${\mathit{T}}_{\mathit{c}}$=216\ifmmode\pm\else\textpm\fi{}1 K, i.e., 35 K above...
We present neutron spin echo experiments that address the much debated topic of dynamic phenomena in polymer melts are induced by interacting with a confining surface. find an anchored surface layer internally is highly mobile and not glassy as heavily promoted literature. The dynamics confinement is, rather, determined two phases, one fully equal to bulk another partly at By strong topological interaction, this phase confines further chains no direct contact These form often invoked...
A systematic study of the equilibrium chain exchange kinetics a tunable model system for starlike polymeric micelles is presented. The are formed by well-defined highly asymmetrical poly(ethylene−propylene)−poly(ethylene oxide) (PEP−PEO) diblock copolymers. Mixtures N,N-dimethylformamide (DMF) and water used as selective solvents PEO. With respect to PEP this solvent mixture allows interfacial tension, γ, be tuned over wide range. between these has been investigated using novel time-resolved...
n-Tritriacontane (n-C33H68) exhibits three solid–solid phase transitions before melting. Applying a variety of experimental techniques, including X-ray scattering, Raman spectroscopy, n.m.r., dielectric relaxation and quasielastic neutron it was possible to specify for all four modifications defect structures the corresponding molecular motions.
We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides different molar masses. The ratio zero-shear viscosities polymer melts η0,linear to their counterparts η0,ring at isofrictional conditions is discussed as a function number entanglements Z. In unentangled regime η0,linear/η0,ring virtually constant, consistent with earlier data, atomistic simulations, theoretical expectation = 2. entanglement regime, Z-dependence viscosity...
The KWS-1 small-angle neutron scattering (SANS) instrument operated by the Jülich Centre for Neutron Science (JCNS) at research reactor FRM II of Heinz Maier-Leibnitz Zentrum in Garching near Munich has been recently upgraded. was updated, from its active collimation apertures to detector cabling. Most parts were installed first time, including a broadband polarizer, large-cross-section radio-frequency spin flipper, chopper and lenses. A custom-designed hexapod sample position allows heavy...
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication the EditorNEXTDynamics of Entangled Chains in Polymer NanocompositesG. J. Schneider*†, K. Nusser*†, L. Willner†, P. Falus‡, and D. Richter†View Author Information† Jülich Centre for Neutron Science Institute Complex Systems, Forschungszentrum GmbH, 52425 Jülich, Germany‡ Institut Laue-Langevin, 6 rue Jules Horowitz, 38000 Grenoble, FranceE-mail: [email protected] (G.J.S.); (K.N.).Cite this: Macromolecules 2011, 44, 15,...
The rheological behavior of poly(ethylene-alt-propylene) (PEP), polydimethylsiloxane (PDMS) and polyisoprene (PI, two molecular weights: 70k 200k) melts containing polyhedral oligomeric silsesquioxane (POSS) molecules was investigated by means small angle scattering (SAXS SANS) oscillatory shear rheology. dependence the nanocomposite viscosity on polymer–particle solubility polymer weight studied. At high filler fractions all polymers exhibited hydrodynamic reinforcement plateau modulus...
Neutron spin echo has revealed the single chain dynamic structure factor of entangled polymer chains confined in cylindrical nanopores with dimensions either much larger or smaller than lateral pore sizes. In both situations, a slowing down dynamics respect to bulk behavior is only observed at intermediate times. The results long times provide direct microscopic measurement entanglement distance under confinement. They constitute first experimental evidence dilution total density melt strong...
Intrinsically disordered proteins lack a well-defined folded structure and contain high degree of structural freedom conformational flexibility, which is expected to enhance binding their physiological targets. In solution in the lipid-free state, myelin basic protein belongs that class proteins. Using small-angle scattering, was found be structurally similar Gaussian chains. The combination hydrodynamic information revealed an intermediary compactness between globular random coil polymers....
Ring polymers have fascinated theorists, simulators, and experimentalists as they are the simplest polymer without ends, giving rise to important topology related properties. We present state of art recent synthetic efforts investigations into structure dynamics dense nonconcatenated ring systems. Analyzing existing knowledge, we identify challenges for future research: In realm synthesis creation well-defined high molecular weight rings based on different monomers highly desirable. field...
We have studied the aggregation behavior of polyethylene−poly(ethylenepropylene) (PE−PEP) diblock copolymers dissolved in decane. For this purpose PE−PEP various molecular weights, compositions, and degrees deuteration were synthesized via an anionic route. The structure morphology aggregates was by small angle neutron scattering varying both contrast as well polymer labeling. found a hierarchy structures: PE component crystallizes lamellar sheets (thickness 40−80 Å) surrounded on sides PEP...
The question of whether the primary $\ensuremath{\alpha}$ relaxation in glass-forming systems is homogeneous or heterogeneous nature investigated by incoherent neutron scattering techniques polymers. It shown that momentum transfer dependence Kohlrausch-Williams-Watts time allows one to discriminate between these two limiting scenarios. From results obtained we can conclude apparent stretching $\ensuremath{\alpha}$-relaxation function relates dominantly sublinear diffusion and not a result...
We have investigated the dynamic structure factor for single-chain relaxation in a polyethylene melt by means of molecular dynamics simulations and neutron spin echo spectroscopy. After accounting 20% difference chain self-diffusion coefficient between simulation experiment we find perfect quantitative agreement intermediate over whole range momentum transfer studied. Based on this one can test experimental results deviations from standard Rouse behavior reported so far only computer polymer...