172 research outputs found
Pushing the glass transition towards random close packing using self-propelled hard spheres
Although the concept of random close packing with an almost universal packing
fraction of ~ 0.64 for hard spheres was introduced more than half a century
ago, there are still ongoing debates. The main difficulty in searching the
densest packing is that states with packing fractions beyond the glass
transition at ~ 0.58 are inherently non-equilibrium systems, where the dynamics
slows down with a structural relaxation time diverging with density; hence, the
random close packing is inaccessible. Here we perform simulations of
self-propelled hard spheres, and we find that with increasing activity the
relaxation dynamics can be sped up by orders of magnitude. The glass transition
shifts to higher packing fractions upon increasing the activity, allowing the
study of sphere packings with fluid-like dynamics at packing fractions close to
random close packing. Our study opens new possibilities of investigating dense
packings and the glass transition in systems of hard particles
Self-consistent field predictions for quenched spherical biocompatible triblock copolymer micelles
We have used the Scheutjens-Fleer self-consistent field (SF-SCF) method to
predict the self-assembly of triblock copolymers with a solvophilic middle
block and sufficiently long solvophobic outer blocks. We model copolymers
consisting of polyethylene oxide (PEO) as solvophilic block and
poly(lactic-co-glycolic) acid (PLGA) or poly({\ko}-caprolactone) (PCL) as
solvophobic block. These copolymers form structurally quenched spherical
micelles provided the solvophilic block is long enough. Predictions are
calibrated on experimental data for micelles composed of PCL-PEO-PCL and
PLGA-PEO-PLGA triblock copolymers prepared via the nanoprecipitation method. We
establish effective interaction parameters that enable us to predict various
micelle properties such as the hydrodynamic size, the aggregation number and
the loading capacity of the micelles for hydrophobic species that are
consistent with experimental finding.Comment: accepted for publication in Soft Matte
Electrostatic hierarchical co-assembly in aqueous solutions of two oppositevely charged double hydrophilic diblock copolymers
peer reviewedThe formation of spherical micelles in aqueous solutions of poly(N-methyl-2-vinyl pyridinium iodide)-block-poly(ethylene oxide), P2MVP-b-PEO and poly(acrylic acid)-block-poly(vinyl alcohol), PAA-b-PVOH has been investigated with light scattering-titrations, dynamic and static light scattering, and 1H 2D Nuclear Overhauser Effect Spectroscopy. Complex coacervate core micelles, also called PIC micelles, block ionomer complexes, and interpolyelectrolyte complexes, are formed in thermodynamic equilibrium under charge neutral conditions (pH 8, 1 mM NaNO3, T = 25 °C) through electrostatic interaction between the core-forming P2MVP and PAA blocks. 2D 1H NOESY NMR experiments show no cross-correlations between PEO and PVOH blocks, indicating their segregation in the micellar corona. Self-consistent field calculations support the conclusion that these C3Ms are likely to resemble a ‘patched micelle’; that is, micelles featuring a ‘spheres-on-sphere’ morphology
Intermittent dynamics in transient polymer networks under shear: Signs of self-organized criticality
Controlled mixing of lanthanide(III) ions in coacervate core micelles
This article presents a facile strategy to combine Eu3+ and Gd3+ ions into coacervate core micelles in a controlled way with a statistical distribution of the ions. Consequently, the formed micelles show a high tunability between luminescence and relaxivity. These highly stable micelles present great potential for new materials, e.g. as bimodal imaging probes
Дослідження енергоефективності будівлі філії "Білопільський РЕМ" ПАТ "Сумиобленерго"
Однією із інноваційних технологій в енергоефективному будівництві є «пасивний будинок», схема обладнання якого була запропонована у 1988 році доктором В. Файстом та професором Б. Адамсоном. «Пасивний будинок» – це споруда, яка не має потреби в опаленні або ж її енергоспоживання становить менше 10 % від енергії на одиницю об’єму, яка споживається більшістю сучасних будівель. Тепло у такому будинку генерується пасивно, тобто лише засобами внутрішніх джерел тепла, сонячної енергії, яка потрапляє через вікна, та шляхом підігрівання повітря, що надходить через вентиляцію. На основі такої схеми обладнання доцільно не лише будувати нові будинки, але й модернізувати старі
Grafted ionomer complexes and their effect on protein adsorption on silica and polysulfone surfaces
We have studied the formation and the stability of ionomer complexes from grafted copolymers (GICs) in solution and the influence of GIC coatings on the adsorption of the proteins β-lactoglobulin (β-lac), bovine serum albumin (BSA), and lysozyme (Lsz) on silica and polysulfone. The GICs consist of the grafted copolymer PAA28-co-PAPEO22 {poly(acrylic acid)-co-poly[acrylate methoxy poly(ethylene oxide)]} with negatively charged AA and neutral APEO groups, and the positively charged homopolymers: P2MVPI43 [poly(N-methyl 2-vinyl pyridinium iodide)] and PAH∙HCl160 [poly(allylamine hydrochloride)]. In solution, these aggregates are characterized by means of dynamic and static light scattering. They appear to be assemblies with hydrodynamic radii of 8 nm (GIC-PAPEO22/P2MVPI43) and 22 nm (GIC-PAPEO22/PAH∙HCl160), respectively. The GICs partly disintegrate in solution at salt concentrations above 10 mM NaCl. Adsorption of GICs and proteins has been studied with fixed angle optical reflectometry at salt concentrations ranging from 1 to 50 mM NaCl. Adsorption of GICs results in high density PEO side chains on the surface. Higher densities were obtained for GICs consisting of PAH∙HCl160 (1.6 ÷ 1.9 chains/nm2) than of P2MVPI43 (0.6 ÷ 1.5 chains/nm2). Both GIC coatings strongly suppress adsorption of all proteins on silica (>90%); however, reduction of protein adsorption on polysulfone depends on the composition of the coating and the type of protein. We observed a moderate reduction of β-lac and Lsz adsorption (>60%). Adsorption of BSA on the GIC-PAPEO22/P2MVPI43 coating is moderately reduced, but on the GIC-PAPEO22/PAH∙HCl160 coating it is enhanced
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