A5024056256- Rheology and Fluid Dynamics Studies
- Material Dynamics and Properties
- Blood properties and coagulation
- Polymer Surface Interaction Studies
- Block Copolymer Self-Assembly
- Medical Imaging Techniques and Applications
- Protein Structure and Dynamics
- Nuclear Physics and Applications
- Advanced X-ray and CT Imaging
- Granular flow and fluidized beds
- High-pressure geophysics and materials
- Nanofabrication and Lithography Techniques
- Advanced Theoretical and Applied Studies in Material Sciences and Geometry
- NMR spectroscopy and applications
- Polymer Science and Applications
- Advanced Thermodynamics and Statistical Mechanics
- Radiation Dose and Imaging
- Polymer crystallization and properties
- Seismic Imaging and Inversion Techniques
- Hydrocarbon exploration and reservoir analysis
- Adhesion, Friction, and Surface Interactions
- Fluid Dynamics and Thin Films
- Force Microscopy Techniques and Applications
- Advanced Polymer Synthesis and Characterization
- X-ray Diffraction in Crystallography
Uppsala University
2018
Institut Laue-Langevin
2016-2018
Laboratoire Interdisciplinaire de Physique
2016-2017
Université Grenoble Alpes
2016-2017
Shear responsive surfaces offer potential advances in a number of applications. Surface functionalization using polymer brushes is one route to such properties, particularly the case entangled polymers. We report on neutron reflectometry measurements solutions performed under controlled shear as well coarse-grained computer simulations corresponding these interfaces. Here we show reversible and reproducible collapse brushes, increasing with rate. Using two greatly different chain lengths...
We present a computer simulation of entangled polymer solutions at equilibrium. The chains repel each other via soft Gaussian potential, appropriate for semi-dilute the scale correlation blob. key innovation to suppress chain crossings is use pseudo-continuous model backbone which effectively leaves no gaps between consecutive points on chain, unlike usual bead-and-spring model. Our algorithm sufficiently fast observe regime using standard desktop computer. simulated structural and...
Grazing incidence neutron scattering experiments offer surface sensitivity by reflecting from an interface at momentum transfers close to total external reflection. Under these conditions the penetration depth is strongly non-linear and may change many orders of magnitude. This fact imposes severe challenges for resolved experiments, since brilliance beams relatively low in comparison e.g. synchrotron radiation. In this article we use probability density functions calculate contribution...
Self-consistent field approach is used to model a single end-tethered polymer chain on substrate subject various forces in three dimensions. Starting from continuous Gaussian model, the following perturbations are considered: (i) hydrodynamic interaction with an externally imposed shear flow for which alternative theoretical framework formulated; (ii) excluded volume effect good solvent, treated mean approximation; (iii) monomer-substrate repulsion. While stretches along flow, change of...
Entangled polymers are deformed by a strong shear flow. The shape of the polymer, called form factor, is measured small angle neutron scattering. However, real-space molecular structure not directly available from reciprocal-space data, due to phase problem. Instead, data has be fitted with theoretical model molecule. We approximate unknown using piecewise straight segments, which we derive an analytical factor. fit it our on semi-dilute entangled polystyrene solution under in situ character...
Particle simulations confined by sharp walls usually develop an oscillatory density profile. For some applications, most notably soft matter liquids, this behavior is often unrealistic and one expects a monotonic climb instead. To reconcile with experiments, we propose mirror-and-shift boundary conditions where each interface mapped to distant part of itself. The main result that the particle increases almost monotonically from zero bulk, over short distance about diameter. method applied...
Abstract X-ray computed tomography (CT) is a commercially established modality for imaging large objects like passenger luggage. CT can provide the density and effective atomic number, which not always sufficient to identify threats explosives narcotics, since they have similar composition benign plastics, glass, or light metals. In these cases, diffraction (XRD) may be better suited distinguish threats. Unfortunately, diffracted photon flux typically much weaker than transmitted one....
The non-linear response of entangled polymers to shear flow is complicated. Its current understanding framed mainly as a rheological description in terms the complex viscosity. However, full picture requires an assessment dynamical structure individual polymer chains which give rise macroscopic observables. Here we shed new light on this problem, using computer simulation based blob model, extended describe melts and semi-dilute solutions. We examine diffusion intermediate scattering spectra...
Star polymers are within the most topologically entangled macromolecules. For a star to move current theory is that one arm must retract branch point. The probability of this event falls exponentially with molecular weight, and quicker relaxation pathway eventually takes over. With simulation over hundred times faster than earlier studies, we demonstrate mean square displacement scales power law 1/16 in time, instead previously assumed zero. It suggests polymer motion result two linear...
Shear flow is known to induce huge density fluctuations in otherwise clear and uniform polymer solutions. This effect rooted the elasticity of entangled network, can span distances over a thousand chains wide. It has been observed many scattering experiments, later explained by mathematical theories. Here we inspect this phenomenon from direct particle simulation viewpoint. The main novelty velocity dependent friction force, coupling entire system solved efficiently with sparse matrix...
A cross-section view into a web of interpenetrated polymer chains is shown. Above the glass transition temperature, molecules are able to diffuse. In article number 1800078, Airidas Korolkovas demonstrates that, for long star-shaped polymers, mean square displacement proportional power law 1/16 time. This particular signature topological entanglement in exactly 5 dimensions.
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