Search results for "rush"

Polymer brushes with reversibly tunable grafting density.

2021

We propose a novel class of responsive polymer brushes, where the effective grafting density can be controlled by external stimuli. This is achieved by using end-grafted polymer chains that have an affinity to the substrate. For sufficiently strong surface interactions, a fraction of chains condenses into a near-surface layer, while the remaining ones form the outer brush. The dense layer and the more tenuous outer brush can be seen as coexisting microphases. The effective grafting density of the outer brush is controlled by the adsorption strength and can be changed reversibly and in a controlled way as a response to changes in environmental parameters. The effect is demonstrated by numeri…

Calcium phosphate/polyvinyl acetate coatings on SS304 via galvanic co-deposition for orthopedic implant applications

2021

Abstract In this work, the galvanic deposition method is used to deposit coatings of brushite/hydroxyapatite/polyvinyl acetate on 304 stainless steel. Coatings are obtained at different temperatures and with different sacrificial anodes, consisting of a mixture of brushite and hydroxyapatite. Samples are aged in a simulated body fluid (SBF), where a complete conversion of brushite into hydroxyapatite with a simultaneous change in morphology and wettability occurred. The corrosion tests show that, compared with bare 304, the coating shifts Ecorr to anodic values and reduces icorr Ecorr, and icorr has different values at different aging times due to chemical interactions at the solid/liquid i…

Polymer-brush lubricated surfaces with colloidal inclusions under shear inversion.

2011

We characterize the response of compressed, sheared polymer-brush bilayers with colloidal inclusions to highly nonstationary inversion processes by means of molecular dynamics simulations and scaling theory. Bilayers with a simple (dimeric) solvent reveal an overshoot for the shear stress, while simulations of dry brushes without explicit solvent molecules fail to display this effect. We demonstrate that mechanical instabilities can be controlled by the inclusion of macromolecular structures, such as colloids of varying softness. Based on a recently developed theory, we suggest a scaling approach to determine a characteristic time for conformational and collective responses.

Polyelectrolyte Brushes Grafted at the Air/Water Interface

1997

A new approach for the study of grafted polyelectrolytes is investigated:  monolayers at the air/water interface of block copolymers consisting of a liquid hydrophobic and a polyelectrolyte block. ...

Particle Penetration into Polydisperse Polymer Brushes: A Theoretical Analysis

2017

Based on theoretical analysis, the effect of polydispersity on particle penetration into polydisperse polymer brushes is investigated. Three different polydispersities representing sharp, moderate, and extremely wide chain length distributions are chosen, since the corresponding explicit expressions of brush density at these polydispersities are available. To simplify the discussion, this study is restricted to spherical particles of small size which ensure that the particle insertion only causes local conformational perturbations. By analyzing the particle distribution, it is found that polydispersity always facilitates particle penetration. This prediction is confirmed by analyzing the su…

Polydisperse polymer brushes: internal structure, critical behavior, and interaction with flow

2016

We study the effect of polydispersity on the structure of polymer brushes by analytical theory, a numerical self-consistent field approach, and Monte Carlo simulations. The polydispersity is represented by the Schulz-Zimm chain-length distribution. We specifically focus on three different polydispersities representing sharp, moderate and extremely wide chain length distributions and derive explicit analytical expressions for the chain end distributions in these brushes. The results are in very good agreement with numerical data obtained with self-consistent field calculations and Monte Carlo simulations. With increasing polydispersity, the brush density profile changes from convex to concav…

Oscillatory interaction between two like‐charged nanoparticles induced by polyelectrolyte brush–solvent interface

2016

Using Copolymers to Design Tunable Stimuli-Reponsive Brushes

2020

Recently, a new design for switch sensors has been proposed that exploits a conformational transition of end-grafted minority adsorption-active homopolymers in a monodisperse polymer brush [Klushin...

Numerical simulations of the dependency of flow pattern on impeller clearance in stirred vessels

2001

The flow and turbulence fields in a fully baffled vessel stirred by a Rushton turbine have been simulated by means of computational fluid dynamics (CFD) techniques. The simulation techniques adopted (the "Sliding-grid" and "Inner-outer" methods) are fully predictive and require no experimental data as boundary or initial conditions. The effect of clearance (C) on the flow patterns in stirred vessels was simulated as the flow field transition observed can be considered a particularly stringent benchmark for the testing of CFD techniques. The results are compared with previously obtained LDA data and show that the double- to single-loop transition experimentally observed when impeller clearan…

Practical Model for Load-Carrying Capacity of Eccentrically Loaded Square Column Footings

2018

In this paper, a practical calculus model based on the strut-and-tie approach for prediction of the load-carrying capacity of eccentrically loaded RC column footings with square cross sections is presented. Existing models based on beam or slab models with flexural and two-way slab punching shear failure are presented and discussed. Several subgrade contact pressure distributions for column footings are considered. A parametric analysis of the effects of footing and column dimensions (depth, width), longitudinal ratio of longitudinal steel, and strength of concrete and steel is made for all models examined. Available experimental data are utilized to verify the model in comparison with exis…