Polymer Brushes in Strong Shear Flow

1996 ◽  
Vol 464 ◽  
Author(s):  
Gary S. Grest
Keyword(s):  
Shear Flow ◽  
Polymer Brushes ◽  
Surface Force ◽  
Polymer Chains ◽  
Radius Of Gyration ◽  
Strong Shear ◽  
Theoretical Predictions ◽  
Self Consistent Field ◽  
Self Consistent Field Theory ◽  
Dynamics Simulations

ABSTRACTPolymers end-grafted to a surface in the presence of a shear flow are studied by molecular dynamics simulations. The solvent velocity field is observed to penetrate only a short distance into the brush consistent with predictions based on self-consistent field theory. The deformation of the brush is small except when the shear rate γ is very large. In this limit, while some of the polymer chains are stretched in the direction of flow, the brush height actually decreases slightly, in contrast to several theoretical predictions. When two surfaces bearing end-grafted chains are brought into contact, the normal force increases rapidly with decreasing plate separation, while the shear force is significantly smaller. For low relative velocity vw of the two walls, the surfaces slide pass each other with almost no change in the chain's radius of gyration or the amount of interpenetration, while for very large vw, there is significant stretching and some disentanglement of the chains. The results are in qualitatively good agreement with recent experiments using the surface force apparatus.

scholarly journals Shear-induced microstructures and dynamics processes of phospholipid cylinders in solutions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yue Shan ◽  
Xiaowei Qiang ◽  
Jianzhu Ye ◽  
Xianghong Wang ◽  
Linli He ◽  
...  
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Cross Sections ◽  
Polymer Chains ◽  
Dynamic Processes ◽  
Radius Of Gyration ◽  
Particle Dynamic ◽  
Shear Direction ◽  
Shape Factors ◽  
Strong Shear

Abstract Shear-induced microstructures and their corresponding dynamic processes are investigated for phospholipid cylinders in aqueous solution by dissipative particle dynamic simulation. Various phospholipid cylinders with cross-sections, which are formed under shear-free flow, are selected to examine the effects of shear flow on their structures and dynamic processes. Shear flow induces the transition from cylinders into vesicles at weak rate and the transition into vesicle–lamella mixtures with increased shear rate and lamella structures at the strong shear rate. Then, the average radius of gyration and shape factors of the polymer chains in the dynamic processes are discussed in detail. Results show that shear flow causes the structure of the polymer chains to be elongated along the shear direction, and the configuration of the polymer chain can be rapidly transformed into an ellipsoid structure under strong shear.

scholarly journals RuSseL: A Self-Consistent Field Theory Code for Inhomogeneous Polymer Interphases

Computation ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 57
Author(s):  
Constantinos J. Revelas ◽  
Aristotelis P. Sgouros ◽  
Apostolos T. Lakkas ◽  
Doros N. Theodorou
Keyword(s):  
Field Theory ◽  
Polymer Melt ◽  
Polymer Chains ◽  
Solid Polymer ◽  
One Dimensional ◽  
Consistent Field ◽  
Adsorbed Polymer ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Self Consistent Field Theory

In this article, we publish the one-dimensional version of our in-house code, RuSseL, which has been developed to address polymeric interfaces through Self-Consistent Field calculations. RuSseL can be used for a wide variety of systems in planar and spherical geometries, such as free films, cavities, adsorbed polymer films, polymer-grafted surfaces, and nanoparticles in melt and vacuum phases. The code includes a wide variety of functional potentials for the description of solid–polymer interactions, allowing the user to tune the density profiles and the degree of wetting by the polymer melt. Based on the solution of the Edwards diffusion equation, the equilibrium structural properties and thermodynamics of polymer melts in contact with solid or gas surfaces can be described. We have extended the formulation of Schmid to investigate systems comprising polymer chains, which are chemically grafted on the solid surfaces. We present important details concerning the iterative scheme required to equilibrate the self-consistent field and provide a thorough description of the code. This article will serve as a technical reference for our works addressing one-dimensional polymer interphases with Self-Consistent Field theory. It has been prepared as a guide to anyone who wishes to reproduce our calculations. To this end, we discuss the current possibilities of the code, its performance, and some thoughts for future extensions.

Exploring Lateral Microphase Separation in Mixed Polymer Brushes by Experiment and Self-Consistent Field Theory Simulations

2011 ◽  
Vol 45 (1) ◽  
pp. 510-524 ◽  
Author(s):  
Andrew D. Price ◽  
Su-Mi Hur ◽  
Glenn H. Fredrickson ◽  
Amalie L. Frischknecht ◽  
Dale L. Huber
Keyword(s):  
Field Theory ◽  
Polymer Brushes ◽  
Microphase Separation ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Self Consistent Field Theory

scholarly journals High-throughput prediction of stress–strain curves of thermoplastic elastomer model block copolymers by combining hierarchical simulation and deep learning

MRS Advances ◽  
2021 ◽  
Author(s):  
Takeshi Aoyagi
Keyword(s):  
Deep Learning ◽  
High Throughput ◽  
High Throughput Screening ◽  
Thermoplastic Elastomer ◽  
Thermoplastic Elastomers ◽  
Coarse Grained ◽  
Stress Strain ◽  
Self Consistent Field ◽  
Self Consistent Field Theory ◽  
Dynamics Simulations

Abstract We achieved high-throughput prediction of the stress–strain (S–S) curves of thermoplastic elastomers by combining hierarchical simulation and deep learning. ABA triblock copolymer with a phase-separated structure was used as a thermoplastic elastomer model. The S–S curves of the ABA triblock copolymers were calculated from the hierarchical simulation of self-consistent field theory calculations and coarse-grained molecular dynamics simulations. Because such hierarchical simulations require considerable computational resources, we applied a deep learning technique to accelerate the prediction. Sets of phase-separated structures and the S–S curves obtained from the hierarchical simulation were used to train a 3D convolutional neural network. Using the trained network, we confirmed that the predicted S–S curves of the untrained structures accurately reproduced the simulation results. These results will enable us to design novel polymers and phase-separated structures with desired S–S curves by high-throughput screening of a wide variety of structures. Graphic abstract

scholarly journals Dual responsive PMEEECL–PAE block copolymers: a computational self-assembly and doxorubicin uptake study

RSC Advances ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 3233-3245 ◽  
Author(s):  
Amin Koochaki ◽  
Mohammad Reza Moghbeli ◽  
Sousa Javan Nikkhah ◽  
Alessandro Ianiro ◽  
Remco Tuinier
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
The Self ◽  
Coarse Grained ◽  
Dual Responsive ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Self Consistent Field Theory ◽  
Dynamics Simulations

The self-assembly behaviour of dual-responsive block copolymers and their ability to solubilize the drug doxorubicin is demonstrated using molecular dynamics simulations, coarse-grained force field simulations and self-consistent field theory.

The Effect of Tacticity and Side Chain Structure on the Coil Dimensions of Polyolefins

2018 ◽  
Author(s):  
Mohammad Atif Faiz Afzal ◽  
Jarod M. Younker ◽  
George Rodriguez
Keyword(s):  
High Throughput Screening ◽  
Waste Water Treatment ◽  
Chain Structure ◽  
Polymer Chains ◽  
Side Chain ◽  
Radius Of Gyration ◽  
Structure Property ◽  
Engine Oils ◽  
Structure Property Relationships ◽  
Dynamics Simulations

<pre>The key to the discovery of materials with targeted properties lies in the understanding of structure-property relationships. In this work, we evaluate the relationship between the polymer structure and their coil dimensions, and explore new polymers based on these relations. Coil dimensions are important features of polymers which affect their performance in various applications, including drug delivery, waste-water treatment, and engine oils. Coil dimensions of the polyolefins are dependent on the number, size, and stereo orientation of side chains along the backbone. Thus, controlling these attributes allows us to tailor the coil dimensions of polyolefins. In the proposed scheme, we calculate the radius of gyration (<i>R<sub>g</sub></i>) of polyolefin chains using molecular dynamics simulations and validate against experimental results. Simulated annealing is implemented to ensure the capture of different configurations. This model affords the ability to quantify the effect tacticity has on the coil dimensions of polyolefins. The results show the suppression of tacticity effects when the polymer chains transition to bottlebrush structures, demonstrating that the side chain steric hindrance plays an important role in the rigidity of the chain backbone. Further, the model is used to evaluate the compositional effects by determining the rigidity of propylene and 1-hexene copolymers. Combining our model with virtual high-throughput screening techniques, we evaluated the coiling behavior of hundreds of new polymers. Using the screening results, we established correlations between the structure of the side chain and the coil dimensions of polymers.</pre><pre>The supplementary material accompanying this paper includes the library of 275 polymers and their corresponding <i>K<sub>s</sub></i> values.<br></pre>

Nanotribological Investigation of the Role of Proteoglycans in Biolubrication

2008 ◽  
Author(s):  
Jasmine Seror ◽  
Nir Kampf ◽  
Alice Maroudas ◽  
Jacob Klein
Keyword(s):  
Polymer Brushes ◽  
Surface Force ◽  
Polymer Chains ◽  
Force Balance ◽  
Superficial Zone ◽  
Prosthetic Devices ◽  
Atomic Force ◽  
Frictional Forces ◽  
Human Joints ◽  
Hydration Layers

Articular joints in human body are uniquely efficient lubrication systems. While the cartilage surfaces slide past each other under physiological working conditions (pressure of tens of atmospheres and shear rates up to 106 – 107 Hz), the friction coefficient (μ) achieves extremely low values (down to 0.001) never successfully reached by mechanical prosthetic devices. Friction studies on polymer brushes attached to surfaces have recently demonstrated (17) their ability to reduce friction between the rubbing surfaces to extremely low values by means of the hydrated ions and the charges on the polymer chains. We propose that the extremely efficient lubrication observed in living joints arises from the presence of a brush-like phase of charged macromolecules at the surface of the cartilage superficial zone: hydration layers which surround the charges on the cartilage macromolecules might provide a lubricating ball-bearing-like effect as demonstrated for the synthetic polyelectrolytes (17). In this work macromolecules of the cartilage superficial zone (aggrecans) are extracted from human femoral heads and purified using well developed biochemical techniques (20). The extracted molecules are then characterized with atomic force microscope (AFM). By means of a surface force balance (SFB) normal and shear interactions between mica surfaces coated with these molecules are examined focusing on the frictional forces between such surfaces at normal stresses similar to those in human joints.

Critical adsorption of a single macromolecule in polymer brushes

Soft Matter ◽  
2014 ◽  
Vol 10 (32) ◽  
pp. 5974-5990 ◽  
Author(s):  
Andrey Milchev ◽  
Sergei A. Egorov ◽  
Kurt Binder
Keyword(s):  
Polymer Brushes ◽  
Density Functional ◽  
Polymer Brush ◽  
Field Theories ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Coated Surfaces ◽  
Dynamics Simulations ◽  
Single Macromolecule

The adsorption of long flexible macromolecules by polymer brush-coated surfaces is studied by molecular dynamics simulations and by calculations using density functional and self-consistent field theories.

scholarly journals Simulation and modelling of slip flow over surfaces grafted with polymer brushes and glycocalyx fibres

2012 ◽  
Vol 711 ◽  
pp. 192-211 ◽  
Author(s):  
Mingge Deng ◽  
Xuejin Li ◽  
Haojun Liang ◽  
Bruce Caswell ◽  
George Em Karniadakis
Keyword(s):  
Shear Rate ◽  
Shear Flow ◽  
Blood Cells ◽  
Polymer Brushes ◽  
Slip Length ◽  
Mesh Size ◽  
Homogeneous Flow ◽  
Strong Shear ◽  
Brush Height ◽  
Scaling Arguments

AbstractFabrication of functionalized surfaces using polymer brushes is a relatively simple process and parallels the presence of glycocalyx filaments coating the luminal surface of our vasculature. In this paper, we perform atomistic-like simulations based on dissipative particle dynamics (DPD) to study both polymer brushes and glycocalyx filaments subject to shear flow, and we apply mean-field theory to extract useful scaling arguments on their response. For polymer brushes, a weak shear flow has no effect on the brush density profile or its height, while the slip length is independent of the shear rate and is of the order of the brush mesh size as a result of screening by hydrodynamic interactions. However, for strong shear flow, the polymer brush is penetrated deeper and is deformed, with a corresponding decrease of the brush height and an increase of the slip length. The transition from the weak to the strong shear regime can be described by a simple ‘blob’ argument, leading to the scaling ${\dot {\gamma } }_{0} \propto {\sigma }^{3/ 2} $, where ${\dot {\gamma } }_{0} $ is the critical transition shear rate and $\sigma $ is the grafting density. Furthermore, in the strong shear regime, we observe a cyclic dynamic motion of individual polymers, causing a reversal in the direction of surface flow. To study the glycocalyx layer, we first assume a homogeneous flow that ignores the discrete effects of blood cells, and we simulate microchannel flows at different flow rates. Surprisingly, we find that, at low Reynolds number, the slip length decreases with the mean flow velocity, unlike the behaviour of polymer brushes, for which the slip length remains constant under similar conditions. (The slip length and brush height are measured with respect to polymer mesh size and polymer contour length, respectively.) We also performed additional DPD simulations of blood flow in a tube with walls having a glycocalyx layer and with the deformable red blood cells modelled accurately at the spectrin level. In this case, a plasma cell-free layer is formed, with thickness more than three times the glycocalyx layer. We then find our scaling arguments based on the homogeneous flow assumption to be valid for this physiologically correct case as well. Taken together, our findings point to the opposing roles of conformational entropy and bending rigidity – dominant effects for the brush and glycocalyx, respectively – which, in turn, lead to different flow characteristics, despite the apparent similarity of the two systems.

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