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Polymer brushes for friction control: Contributions of molecular simulations. Biointerphases 2023; 18:010801. [PMID: 36653299 DOI: 10.1116/6.0002310] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
When polymer chains are grafted to solid surfaces at sufficiently high density, they form brushes that can modify the surface properties. In particular, polymer brushes are increasingly being used to reduce friction in water-lubricated systems close to the very low levels found in natural systems, such as synovial joints. New types of polymer brush are continually being developed to improve with lower friction and adhesion, as well as higher load-bearing capacities. To complement experimental studies, molecular simulations are increasingly being used to help to understand how polymer brushes reduce friction. In this paper, we review how molecular simulations of polymer brush friction have progressed from very simple coarse-grained models toward more detailed models that can capture the effects of brush topology and chemistry as well as electrostatic interactions for polyelectrolyte brushes. We pay particular attention to studies that have attempted to match experimental friction data of polymer brush bilayers to results obtained using molecular simulations. We also critically look at the remaining challenges and key limitations to overcome and propose future modifications that could potentially improve agreement with experimental studies, thus enabling molecular simulations to be used predictively to modify the brush structure for optimal friction reduction.
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Trejos VM, Pizio O, Sokołowski S. On the interdigitation of molecular brushes and solvation force upon adsorption of water in slit-like pores with grafted chains. Density functional approach. J Chem Phys 2019. [DOI: 10.1063/1.5116128] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- Víctor M. Trejos
- Instituto de Ciencias Básicas e Ingeniería, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo Km. 4.5, Col. Carboneras, C.P. 42184, Mineral de la Reforma, Hidalgo, Mexico
| | - Orest Pizio
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, 04510, Cd. de México, Mexico
| | - Stefan Sokołowski
- Department for the Modelling of Physico-Chemical Processes, Maria Curie-Skłodowska University, Lublin 20-031, Poland
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Nguyen VP, Phi PQ, Choi ST. Tribological Behavior of Grafted Nanoparticle on Polymer-Brushed Walls: A Dissipative Particle Dynamics Study. ACS APPLIED MATERIALS & INTERFACES 2019; 11:11988-11998. [PMID: 30821436 DOI: 10.1021/acsami.8b19001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Two contacting surfaces grafted with polymer brushes have potential applications due to their extraordinary lubricating behavior. However, the polymer brushes may have poor mechanical stability under high normal and shear stresses, which is a challenge for practical usage of polymer brush systems. In this study, we propose the use of grafted nanoparticles as nanobearings on polymer-brush-coated surfaces to alleviate the harsh working conditions of polymer brushes and to improve their mechanical stability. We have performed dissipative particle dynamics (DPD) simulations to investigate the tribological interaction between grafted nanoparticle and parallel walls with noncharged polymer brushes in the presence of explicit solvent. The influences of several parameters (solvent quality, brush miscibility, etc.) on the tribological behavior of the system are investigated. The grafted nanoparticle obviously acts as a nanobearing that partially replaces the sliding contact between two brushed walls with rolling contact between the grafted nanoparticle and two brushed walls and reduces the number of DPD particles withstanding high force. Although the introduction of the grafted nanoparticle into polymer-brushed walls increases the friction coefficient by 20-30%, it does not greatly decrease lubrication of the brushed walls, while still helping in stabilizing the system of polymer brushes to be used with liquids with low viscosity, such as water. The DPD simulation results and analysis performed in this study would be beneficial in designing systems with polymer-brushed surfaces and grafted nanoparticles.
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Affiliation(s)
- Vinh Phu Nguyen
- School of Mechanical Engineering , Chung-Ang University , 84 Heukseok-Ro , Dongjak-Gu, Seoul 06974 , Republic of Korea
| | - Phuoc Quang Phi
- School of Mechanical Engineering , Chung-Ang University , 84 Heukseok-Ro , Dongjak-Gu, Seoul 06974 , Republic of Korea
| | - Seung Tae Choi
- School of Mechanical Engineering , Chung-Ang University , 84 Heukseok-Ro , Dongjak-Gu, Seoul 06974 , Republic of Korea
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Desai PR, Das S. Lubrication in polymer-brush bilayers in the weak interpenetration regime: Molecular dynamics simulations and scaling theories. Phys Rev E 2018; 98:022503. [PMID: 30253630 DOI: 10.1103/physreve.98.022503] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Indexed: 11/06/2022]
Abstract
We conduct molecular dynamics (MD) simulations and develop scaling laws to quantify the lubrication behavior of weakly interpenetrated polymer brush bilayers in the presence of an external shear force. The weakly interpenetrated regime is characterized by 1<d_{g}/d_{0}<2, where d_{g} is the gap between the opposing surfaces (where the brushes are grafted) and d_{0} is the unperturbed brush height. MD simulations predict that in the shear thinning regime, characterized by a larger shear force or a large Weissenberg number (W), R_{g}^{2}∼W^{0.19} and η∼W^{-0.38}, where R_{g} is the chain extension in the direction of the shear and η is the viscosity. These scaling behaviors, which are distinctly different from that witnessed in strongly compressed regime (for such a regime, characterized by d_{g}/d_{0}<1, R_{g}^{2}∼W^{0.53}, and η∼W^{-0.46}), match excellently with those predicted by our scaling theory.
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Affiliation(s)
- Parth Rakesh Desai
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
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Desai PR, Sinha S, Das S. Polyelectrolyte brush bilayers in weak interpenetration regime: Scaling theory and molecular dynamics simulations. Phys Rev E 2018; 97:032503. [PMID: 29776032 DOI: 10.1103/physreve.97.032503] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Indexed: 06/08/2023]
Abstract
We employ molecular dynamics (MD) simulations and develop scaling theories to quantify the equilibrium behavior of polyelectrolyte (PE) brush bilayers (BBLs) in the weakly interpenetrated regime, which is characterized by d_{0}<d_{g}<2d_{0}, where d_{g} is the gap between the opposing plates where the PE brushes are grafted and d_{0} is the unperturbed height of a PE brush grafted at a single plate. Scaling predictions establish that, for the weakly interpenetrated osmotic PE BBLs δ∼N^{1/2}(2-d_{g}/d_{0})^{1/2} (where δ is the interpenetration length and N is the number of Kuhn segments in PE brush). MD simulations excellently recover this dependence of δ on N and the extent of interpenetration (quantified by d_{g}/d_{0}). These predictions, unlike the existing studies, establish a finite interpenetration for all values of d_{g}/d_{0} as long as d_{g}<2d_{0}. Finally, we quantify the monomer and counterion concentration distributions and point out that these two distributions may quantitatively deviate from each other at locations very close to the channel centerline, where the interpenetration-induced monomer concentration can be significantly low.
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Affiliation(s)
- Parth Rakesh Desai
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Shayandev Sinha
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
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Hernández Velázquez J, Mejía-Rosales S, Gama Goicochea A. Nanorheology of poly - and monodispersed polymer brushes under oscillatory flow as models of epithelial cancerous and healthy cell brushes. POLYMER 2017. [DOI: 10.1016/j.polymer.2017.09.046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Desai PR, Sinha S, Das S. Compression of polymer brushes in the weak interpenetration regime: scaling theory and molecular dynamics simulations. SOFT MATTER 2017; 13:4159-4166. [PMID: 28555684 DOI: 10.1039/c7sm00466d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We employ scaling theory and Molecular Dynamics (MD) simulations to probe the compression of the semi-dilute polymer brush bilayers (BBLs) in the weak interpenetration (IP) regime. Such a regime is characterized by two layers of interacting polymer brushes grafted on opposing planar surfaces having a separation dg, such that d0 < dg < 2d0, with d0 being the unperturbed brush height. Currently, scaling theories are known for polymer BBLs with a much larger degree of IP (i.e., dg < d0) - in such regimes, the brush height can be quantified by the corresponding IP length δ. On the other hand, we show that in the weak IP regime, the brush height is not solely dictated by δ. We develop new scaling theories to show that δ in this weak IP regime is different from that in the strong IP regime. Secondly, we establish that the compressed brush height in this weakly IP regime can be described as d ∼ Nχ with χ < 1 and varying monotonically with dg/d0. MD simulations are carried out to quantify δ and χ and the results match excellently with our new scaling theory predictions. Finally, we establish that our scaling theory can reasonably predict the experimentally witnessed variation of the interaction energy dictating the compressive force between the interpenetrating brushes in this weakly IP regime.
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Affiliation(s)
- Parth Rakesh Desai
- Department of Mechanical Engineering, University of Maryland, College Park, MD-20742, USA.
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Kreer T. Polymer-brush lubrication: a review of recent theoretical advances. SOFT MATTER 2016; 12:3479-3501. [PMID: 27029521 DOI: 10.1039/c5sm02919h] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This review compiles recent theoretical advances to describe compressive and shear forces of polymer-brush bilayers, which consist of two opposing brushes in contact. Such model systems for polymer-brush lubrication are frequently used as a benchmark to gain insight into biological problems, e.g., synovial joint lubrication. Based on scaling theory, I derive conformational and collective properties of polymer-brush bilayers in equilibrium and out-of-equilibrium situations, such as shear forces in the linear and nonlinear response regimes of stationary shear and under non-stationary shear. Furthermore, I discuss the influence of macromolecular inclusions and electrostatic interactions on polymer-brush lubrication. Comparisons to alternative analytical approaches, experiments and numerical results are performed. Special emphasis is given to methods for simulating polymer-brush bilayers using molecular dynamics simulations.
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Affiliation(s)
- T Kreer
- Leibniz-Institut für Polymerforschung Dresden, Hohe Straße 6, 01069 Dresden, Germany.
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de Beer S, Mensink LIS, Kieviet BD. Geometry-Dependent Insertion Forces on Particles in Swollen Polymer Brushes. Macromolecules 2016. [DOI: 10.1021/acs.macromol.5b01960] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Sissi de Beer
- Materials Science and Technology
of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Liz I. S. Mensink
- Materials Science and Technology
of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Bernard D. Kieviet
- Materials Science and Technology
of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Neratova IV, Kreer T, Sommer JU. Translocation of Molecules with Different Architectures through a Brush-Covered Microchannel. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Irina V. Neratova
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany
- Institut
für Theoretische Physik, Technische Universität Dresden, Zellescher Weg 17, D-01069 Dresden, Germany
| | - Torsten Kreer
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany
| | - Jens-Uwe Sommer
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany
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11
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de Beer S. Switchable friction using contacts of stimulus-responsive and nonresponding swollen polymer brushes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8085-8090. [PMID: 24954240 DOI: 10.1021/la5013473] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Stimulus-responsive (SR), solvated polymers can switch between an expanded state and a collapsed state via external stimuli. Using molecular dynamics simulations, I show that such SR polymers can be employed to control the frictional response between two opposing polymer brushes in relative sliding motion. By using a brush composed of SR polymers in contact with a nonresponding solvated polymer brush, the presence of capillaries and the overlap between molecules of the opposing brushes can be switched. When both brushes are solvated, a capillary is formed and polymers of the opposing brushes interdigitate. Interdigitation dominates friction upon shearing flat brush-bearing surfaces, while the breaking and formation of capillaries dominate friction in the low-velocity limit between rough brush-bearing surfaces. Thus, when either rough or flat polymer-bearing surfaces are sheared, friction between two swollen brushes can be high. In contrast, when the SR brush is collapsed, the solvent absorbs only in the brush that does not respond to the external stimulus. The latter circumvents the presence of capillaries and interdigitation of the brushes, which results in a low friction force upon shearing.
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Affiliation(s)
- Sissi de Beer
- Jülich Supercomputing Centre, Forschungszentrum Jülich , Jülich, Germany
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12
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Solvent-induced immiscibility of polymer brushes eliminates dissipation channels. Nat Commun 2014; 5:3781. [DOI: 10.1038/ncomms4781] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 04/01/2014] [Indexed: 11/08/2022] Open
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Abstract
We present a novel scaling theory to describe the interaction free energy within a compressed polymer-brush bilayer. For semidilute brushes at intermediate and strong compressions, we predict that the interaction free energy scales with distance, D, between the grafting surfaces as A(D) ∼ D-2.5; i.e., the repulsive force, f(D) ∼ D-3.5, measured at the surfaces increases more strongly upon compression than predicted by the classical theory of Milner, Witten, and Cates. We find good agreement with experimental data and excellent agreement with numerical results, which follow our analytical predictions over a wide range of surface separations. The theory is based on the assumption of a strong correlation of the repulsive force and the interpenetration between the brushes. Using our numerical data, we can demonstrate this correlation with great precision.
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Affiliation(s)
- T. Kreer
- Leibniz-Institut für Polymerforschung (IPF) Dresden, Hohe Straße 6, 01069 Dresden, Germany
| | - S.M. Balko
- Max-Bergmann Zentrum für Biomaterialien (MBZ) am IPF, Hohe Straße 6, 01069 Dresden, Germany
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Balko SM, Kreer T, Costanzo PJ, Patten TE, Johner A, Kuhl TL, Marques CM. Polymer brushes under high load. PLoS One 2013; 8:e58392. [PMID: 23516470 PMCID: PMC3596396 DOI: 10.1371/journal.pone.0058392] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Accepted: 02/04/2013] [Indexed: 11/25/2022] Open
Abstract
Polymer coatings are frequently used to provide repulsive forces between surfaces in solution. After 25 years of design and study, a quantitative model to explain and predict repulsion under strong compression is still lacking. Here, we combine experiments, simulations, and theory to study polymer coatings under high loads and demonstrate a validated model for the repulsive forces, proposing that this universal behavior can be predicted from the polymer solution properties.
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Affiliation(s)
- Suzanne M. Balko
- Department of Chemical Engineering and Materials Science, University of California Davis, Davis, California, United States of America
- Leibniz-Institut für Polymerforschung Dresden e.V., Dresden, Germany
| | - Torsten Kreer
- Leibniz-Institut für Polymerforschung Dresden e.V., Dresden, Germany
| | - Philip J. Costanzo
- Department of Chemistry, University of California Davis, Davis, California, United States of America
| | - Tim E. Patten
- Department of Chemistry, University of California Davis, Davis, California, United States of America
| | - Albert Johner
- Institut Charles Sadron, Université de Strasbourg, CNRS, Strasbourg, France
| | - Tonya L. Kuhl
- Department of Chemical Engineering and Materials Science, University of California Davis, Davis, California, United States of America
| | - Carlos M. Marques
- Institut Charles Sadron, Université de Strasbourg, CNRS, Strasbourg, France
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Binder K, Milchev A. Polymer brushes on flat and curved surfaces: How computer simulations can help to test theories and to interpret experiments. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/polb.23168] [Citation(s) in RCA: 166] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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