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Zhang LL, Zhao Y, Li KX, Yu SS, Dong RZ, Ma SH, Liu H, Xing LB, Zhou F. Bioinspired simultaneous regulation in fluorescence of AIEgen-embedded hydrogels. SOFT MATTER 2023; 19:7093-7099. [PMID: 37681740 DOI: 10.1039/d3sm00845b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
The development of stimuli-responsive functional fluorescent hydrogels is of great significance for the realization of artificial intelligence. In the present work, we design and synthesize a stimulus-responsive hydrogel embedded with an aggregation-induced emission (AIE) monomer, in which the fluorescence brightness and intensity can be tuned. The hydrogel embedded with tetraphenylethene-grafted-poly[3-sulfopropyl methacrylate potassium salt] (TPE-PSPMA) as the functional element is prepared by the radical polymerization method. Among them, the TPE core exhibits adaptive fluorescence ability through the AIE effect, while the PSPMA chain provides tunable hydrophilic properties under an external stimulus. The effect of different cationic surfactants with different lengths of hydrophobic tails on the fluorescence properties of TPE-PSPMA in solution is systematically investigated. With cationic surfactants, such as cetyltrimethylammonium bromide (CTAB), the fluorescence intensity is gradually tuned from 1059 to 4623. And the fluorescence intensities increase with the growth of hydrophobic tails of surfactants, which results from hydrophobicity-induced electrostatic interactions among surfactants and polymer chains. Furthermore, an obvious tunable fluorescence feature of hydrogel copolymerized TPE-PSPMA is realized, resulting from the change of brightness and the dynamic increase of fluorescence intensity (from 1031 to 3138) for the hydrogel immersed in CTAB solution with different soaking times. Such a typical fluorescence-regulated behavior can be attributed to the AIE of the TPE-PSPMA chain and the electrostatic interaction between the surfactant and the anionic polymer chain. The designed TPE-PSPMA-based hydrogel is responsive to stimuli, inspiring the development of intelligent systems such as soft robots and smart wearables.
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Affiliation(s)
- Li-Li Zhang
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
| | - Yu Zhao
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
| | - Ke-Xin Li
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
| | - Sheng-Sheng Yu
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
| | - Rui-Zhi Dong
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
| | - Shuan-Hong Ma
- Shandong Laboratory of Yantai Advanced Materials and Green Manufacture, Yantai 264006, P. R. China
| | - Hui Liu
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
- State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences, Lanzhou 730000, P. R. China
| | - Ling-Bao Xing
- School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo 255000, P. R. China.
| | - Feng Zhou
- State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences, Lanzhou 730000, P. R. China
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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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Luo Y, Pang AP, Lu X. Liquid-Solid Interfaces under Dynamic Shear Flow: Recent Insights into the Interfacial Slip. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:4473-4482. [PMID: 35377658 DOI: 10.1021/acs.langmuir.2c00037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The development of micro/nanofluidic techniques has recently revived interest in dynamic shear flow at liquid-solid interfaces. When the nature of the liquid-solid boundaries was revisited, the slip of the fluids relative to the solid wall was predicted theoretically and confirmed experimentally. This indicates that the molecular-level structures of the liquid-solid interfaces will be influenced by the liquid flow over certain temporal and spatial criteria. However, the fluid flow at the boundary layer still cannot be precisely predicted and effectively controlled, somehow limiting its practical applications. Here, we summarize the recent advances for the microscopic structures at the liquid-solid interfaces upon shear flow. Special attention was given to a second-order nonlinear optical technique, sum frequency generation vibrational spectroscopy, which is a powerful tool for exploring the molecular-level structures and structural dynamics at the liquid-solid interfaces and offering new insights into the molecular mechanisms of the fluid slip at the interfaces. Moreover, we discuss the possible approaches for controlling the interfacial slip at the molecular level and highlight the current challenges and opportunities. Although the theoretical framework of the slip at the liquid-solid interfaces is still incomplete, we hope that this Perspective will complement and enhance our understanding of various interfacial properties and phenomena with respect to practical non-equilibrium dynamic processes happening at the interfaces.
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Affiliation(s)
- Yongsheng Luo
- The State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu, P. R. China
| | - Ai-Ping Pang
- The State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu, P. R. China
| | - Xiaolin Lu
- The State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu, P. R. China
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Luo Y, Pang AP, Zhu P, Wang D, Lu X. Demonstrating the Interfacial Polymer Thermal Transition from Coil-to-Globule to Coil-to-Stretch under Shear Flow Using SFG and MD Simulation. J Phys Chem Lett 2022; 13:1617-1627. [PMID: 35142518 DOI: 10.1021/acs.jpclett.1c03866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Revealing interfacial shear-induced structural responsiveness has long been an important topic in that most fluids in nature and human life are in motion and cause interesting boundary phenomena. It is amazing how the polymer chain conformation or local structural features at a boundary change under the effective shear condition. In this study, microfluidic-assisted sum frequency generation (SFG) vibrational spectroscopy and all-atom molecular dynamics (MD) simulation are combined to reveal that the shear flow can effectively block the so-called thermal coil-to-globule transition of the poly(N-isopropylacrylamide) (PNIPAM) brushes on the solid substrate, and the normal coil-to-globule transition transfers to a coil-to-stretch one under shear flow with increasing ambient temperature. Such findings are attributed to the balance between the shear flow and the molecular interaction with respect to the polymer chains and adjacent water molecules, thus demonstrating the significant effect of the shear flow on the structural and dynamic behaviors of the polymer chains at the boundaries from the molecular level.
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Affiliation(s)
- Yongsheng Luo
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu Province, P. R. China
| | - Ai-Ping Pang
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu Province, P. R. China
| | - Peizhi Zhu
- College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225009, Jiangsu Province, P. R. China
| | - Dayang Wang
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, Jilin Province, P. R. China
| | - Xiaolin Lu
- State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, Jiangsu Province, P. R. China
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Jungmann P, Kreer T, Sommer JU, Paturej J. Conformational Properties of End-Grafted Bottlebrush Polymers. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01586] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Paul Jungmann
- Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany
| | - Torsten Kreer
- Institut für Physik, Johannes Gutenberg-Universitä, 55128 Mainz, Germany
| | - Jens-Uwe Sommer
- Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany
- Institute for Theoretical Physics, Technische Universität Dresden, 01069 Dresden, Germany
| | - Jarosław Paturej
- Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany
- Institute of Physics, University of Silesia, 41-500 Chorzów, Poland
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6
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Zhulina EB, Neelov IM, Sheiko SS, Borisov OV. Planar Brush of End-Tethered Molecular Bottle-Brushes. Scaling Mode. POLYMER SCIENCE SERIES C 2018. [DOI: 10.1134/s1811238218020236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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7
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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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8
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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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9
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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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10
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11
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Ramakrishna SN, Cirelli M, Divandari M, Benetti EM. Effects of Lateral Deformation by Thermoresponsive Polymer Brushes on the Measured Friction Forces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4164-4171. [PMID: 28394137 DOI: 10.1021/acs.langmuir.7b00217] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The nanotribological properties of hydrophilic polymer brushes are conveniently analyzed by lateral force microscopy (LFM). However, the measurement of friction for highly swollen and relatively thick polymer brushes can be strongly affected by the tendency of the compliant brush to be laterally deformed by the shearing probe. This phenomenon induces a "tilting" in the recorded friction loops, which is generated by the lateral bending and stretching of the grafts. In this study we highlight how the brush lateral deformation mainly affects the friction measurements of swollen PNIPAM brushes (below LCST) when relatively short scanning distances are applied. Under these conditions, the energy dissipation recorded by LFM is almost uniquely determined by stretching and bending of the compliant brush back and forth along the scanning direction, and it is not correlated to dynamic friction between two sliding surfaces. In contrast, when the scanning distance applied during LFM is relevantly longer than the brush lateral deformation, sliding of the probe on the brush interface becomes dominant, and a correct measurement of dynamic friction can be accomplished. By increasing the temperature above the LCST, the PNIPAM brushes undergo dehydration and assume a collapsed morphology, thereby hindering their lateral deformation by scanning probe. Hence, at 40 °C in water the recorded friction loops do not show any tilting and LFM accurately describes the dynamic friction between the probe and the polymer surface.
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Affiliation(s)
- Shivaprakash N Ramakrishna
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5/10, 8093 Zurich, Switzerland
| | - Marco Cirelli
- Department of Materials Science and Technology of Polymers, MESA + Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Mohammad Divandari
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5/10, 8093 Zurich, Switzerland
| | - Edmondo M Benetti
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5/10, 8093 Zurich, Switzerland
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12
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Singh MK, Ilg P, Espinosa-Marzal RM, Spencer ND, Kröger M. Influence of Chain Stiffness, Grafting Density and Normal Load on the Tribological and Structural Behavior of Polymer Brushes: A Nonequilibrium-Molecular-Dynamics Study. Polymers (Basel) 2016; 8:E254. [PMID: 30974530 PMCID: PMC6431904 DOI: 10.3390/polym8070254] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 06/24/2016] [Accepted: 07/01/2016] [Indexed: 12/16/2022] Open
Abstract
We have performed coarse-grained molecular-dynamics simulations on both flexible and semiflexible multi-bead-spring model polymer brushes in the presence of explicit solvent particles, to explore their tribological and structural behaviors. The effect of stiffness and tethering density on equilibrium-brush height is seen to be well reproduced within a Flory-type theory. After discussing the equilibrium behavior of the model brushes, we first study the shearing behavior of flexible chains at different grafting densities covering brush and mushroom regimes. Next, we focus on the effect of chain stiffness on the tribological behavior of polymer brushes. The tribological properties are interpreted by means of the simultaneously recorded density profiles. We find that the friction coefficient decreases with increasing persistence length, both in velocity and separation-dependency studies, over the stiffness range explored in this work.
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Affiliation(s)
- Manjesh K Singh
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
| | - Patrick Ilg
- School of Mathematical and Physical Sciences, University of Reading, Reading RG6 6AX, UK.
| | - Rosa M Espinosa-Marzal
- Laboratory for Smart Interfaces in Environmental Nanotechnology, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801, USA.
| | - Nicholas D Spencer
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
| | - Martin Kröger
- Polymer Physics, Department of Materials, ETH Zurich, CH⁻8093 Zurich, Switzerland.
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13
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Leuty GM, Tsige M, Grest GS, Rubinstein M. Tension Amplification in Tethered Layers of Bottle-Brush Polymers. Macromolecules 2016; 49:1950-1960. [PMID: 27695137 PMCID: PMC5040463 DOI: 10.1021/acs.macromol.5b02305] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Molecular dynamics simulations of a coarse-grained bead-spring model have been used to study the effects of molecular crowding on the accumulation of tension in the backbone of bottle-brush polymers tethered to a flat substrate. The number of bottle-brushes per unit surface area, Σ, as well as the lengths of the bottle-brush backbones Nbb (50 ≤ Nbb ≤ 200) and side chains Nsc (50 ≤ Nsc ≤ 200) were varied to determine how the dimensions and degree of crowding of bottle-brushes give rise to bond tension amplification along the backbone, especially near the substrate. From these simulations, we have identified three separate regimes of tension. For low Σ, the tension is due solely to intramolecular interactions and is dominated by the side chain repulsion that governs the lateral brush dimensions. With increasing Σ, the interactions between bottle-brush polymers induce compression of the side chains, transmitting increasing tension to the backbone. For large Σ, intermolecular side chain repulsion increases, forcing side chain extension and reorientation in the direction normal to the surface and transmitting considerable tension to the backbone.
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Affiliation(s)
- Gary M. Leuty
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Mesfin Tsige
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Gary S. Grest
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Michael Rubinstein
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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14
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Klein C, Iacovella CR, McCabe C, Cummings PT. Tunable transition from hydration to monomer-supported lubrication in zwitterionic monolayers revealed by molecular dynamics simulation. SOFT MATTER 2015; 11:3340-3346. [PMID: 25790338 DOI: 10.1039/c4sm02883j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The tribology of 2-methacryloyloxyethyl phosphorylcholine monolayers in water is studied using molecular dynamics simulations. Our results show two distinct shear regimes where the first is dominated by hydration lubrication, exhibiting near zero friction coefficients, and the second by chain-chain interactions, resembling monomer-supported lubrication. These results provide insight into the hydration lubrication mechanism - a phenomena thought to underlie the extremely efficient lubrication provided by surfaces functionalized with polyzwitterionic polymer brushes and the mammalian synovial joint.
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Affiliation(s)
- Christoph Klein
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA.
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15
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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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16
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Abstract
Friction between ring polymer brush bilayers sliding past each other at melt densities is studied using extensive coarse-grained molecular dynamics simulations and scaling arguments, and the results are compared to the friction between bilayers of linear polymer brushes. We show that for a velocity range spanning over three decades, the frictional forces measured for ring polymer brushes are half of the corresponding friction in the case of linear brushes. In the linear-force regime, the weak inter-digitation between ring brush layers as compared to linear brushes leads also to a lower number of binary collisions between the monomers from opposing brushes. At high velocities, where the thickness of the inter-digitation between bilayers is on the order of monomer size regardless of brush topology, stretched segments of ring polymers adopt the double-stranded conformation. As a result, monomers of the double-stranded segments collide on average less with the monomers of the opposing ring brush even though a similar number of monomers occupies the inter-digitation layer for ring and linear brush bilayers. The numerical data obtained from our simulations are consistent with the proposed scaling analysis. Conformation-dependent friction reduction observed in ring brushes can have important consequences in non-equilibrium bulk systems.
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Affiliation(s)
- Aykut Erbaş
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.
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17
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Borges J, Mano JF. Molecular Interactions Driving the Layer-by-Layer Assembly of Multilayers. Chem Rev 2014; 114:8883-942. [DOI: 10.1021/cr400531v] [Citation(s) in RCA: 609] [Impact Index Per Article: 60.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- João Borges
- 3B’s
Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Zona Industrial da Gandra,
S. Cláudio do Barco 4806-909 Caldas das Taipas, Guimarães, Portugal
- ICVS/3B’s
− PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - João F. Mano
- 3B’s
Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, Zona Industrial da Gandra,
S. Cláudio do Barco 4806-909 Caldas das Taipas, Guimarães, Portugal
- ICVS/3B’s
− PT Government Associate Laboratory, Braga/Guimarães, Portugal
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18
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LeBard DN. Advancing simulations of biological materials: applications of coarse-grained models on graphics processing unit hardware. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2014.899700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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19
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Doig M, Warrens CP, Camp PJ. Structure and friction of stearic acid and oleic acid films adsorbed on iron oxide surfaces in squalane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:186-195. [PMID: 24364665 DOI: 10.1021/la404024v] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The structure and friction of fatty acid surfactant films adsorbed on iron oxide surfaces lubricated by squalane are examined using large-scale molecular dynamics simulations. The structures of stearic acid and oleic acid films under static and shear conditions, and at various surface coverages, are described in detail, and the effects of unsaturation in the tail group are highlighted. At high surface coverage, the measured properties of stearic acid and oleic acid films are seen to be very similar. At low and intermediate surface coverages, the presence of a double bond, as in oleic acid, is seen to give rise to less penetration of lubricant in to the surfactant film and less layering of the lubricant near to the film. The kinetic friction coefficient is measured as a function of shear rate within the hydrodynamic (high shear rate) lubrication regime. Lubricant penetration and layering are observed to be correlated with friction coefficient. The friction coefficient with oleic acid depends only weakly on surface coverage, while stearic acid admits more lubricant penetration, and its friction coefficient increases significantly with decreasing surface coverage. Connections between film structure and friction are discussed.
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Affiliation(s)
- Michael Doig
- School of Chemistry, University of Edinburgh , West Mains Road, Edinburgh EH9 3JJ, Scotland
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Goicochea AG, Mayoral E, Klapp J, Pastorino C. Nanotribology of biopolymer brushes in aqueous solution using dissipative particle dynamics simulations: an application to PEG covered liposomes in a theta solvent. SOFT MATTER 2014; 10:166-174. [PMID: 24652222 DOI: 10.1039/c3sm52486h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We undertake the investigation of sheared polymer chains grafted onto flat surfaces to model liposomes covered with polyethylene glycol brushes as a case study for the mechanisms of efficient drug delivery in biologically relevant situations, for example, as carriers for topical treatments of illnesses in the human vasculature. For these applications, specific rheological properties are required, such as low viscosity at high shear rates, to improve the transport of the liposomes. Therefore, extensive non-equilibrium, coarse-grained dissipative particle dynamics simulations of polymer brushes of various lengths and shear rates are performed to obtain the average viscosity and the friction coefficient of the system as functions of the shear rate and polymerization degree under theta-solvent conditions, and we find that the brushes experience considerable shear thinning at large shear rates. The viscosity (η) and the friction coefficient (μ) are shown to obey the scaling laws η ∼ γ dot above (-0.31) and μ ∼ γ dot above (0.69) at high shear rates (γ dot above) in a theta solvent, irrespective of the degree of polymerization of brushes. These results confirm recent scaling predictions and reproduce very well trends in measurements of the viscosity at a high shear rate (γ dot above) of red blood cells in a liposome containing medium.
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Affiliation(s)
- A Gama Goicochea
- Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, La Marquesa Ocoyoacac, Estado de México 52750, Mexico.
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22
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Wernersson E, Linse P. Spreading and brush formation by end-grafted bottle-brush polymers with adsorbing side chains. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:10455-10462. [PMID: 23924341 DOI: 10.1021/la4021959] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We investigate structural and thermodynamic properties of surface-grafted layers of model "bottle-brush" polymers by Monte Carlo simulation. The polymers consist of a longer main chain densely grafted with shorter side chains, of which the latter have some degree of affinity to the surface. Our focus is on the effect of the side-chain surface affinity on the brush properties, which we study in terms of compression isotherms spanning a broad range of grafting densities. For low grafting densities, side-chain adsorption causes the polymers to spread on the surface. As the grafting density is increased, the layer goes through a "pancake-to-brush" transition to form a brush with the main chains aligned perpendicular to the surface. We find that side-chain adsorption is decisive for the structure of dilute layers and in the transition region but has little influence on the properties of dense brushes. The close relation between compression and adsorption isotherms is discussed, and the implications of side-chain adsorption for the ability of the polymer to form a dense brush are investigated. This analysis suggests that side-chain surface affinity alone will not give rise to "brush of bottle-brushes" layers by adsorption of polymers from solution, in agreement with recent experimental results.
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Affiliation(s)
- Erik Wernersson
- Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
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23
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Abstract
By means of molecular dynamics simulations we provide evidence for pronounced counterion immobilization in strongly compressed polyelectrolyte-brush bilayers, where the counterions represent the vast majority of mobile solvent particles. As a consequence, hydrodynamic effects are strongly suppressed and semidilute bilayers can respond to shear motion like electrically neutral bilayers at melt density. For large, time-independent shear rates, γ̇, the shear force scales as f(γ̇) ∼ γ̇0.69, in agreement with scaling theory. In this regime, polyelectrolyte-brush bilayers can stabilize highly nonstationary processes, such as the instantaneous inversion of the shear direction. The absence of hydrodynamic flow leads to a suppression of the overshoot for the shear force, which is found for electrically neutral bilayers with the same molecular parameters. We suggest that nature uses this mechanism to optimize biolubrication, for instance in synovial joints.
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Affiliation(s)
- L. Spirin
- Graduate School Materials Science in Mainz, Staudingerweg 9, 55128 Mainz,
Germany
- Leibniz Institut für Polymerforschung Dresden, Hohe Straße
6, 01069 Dresden, Germany
| | - T. Kreer
- Leibniz Institut für Polymerforschung Dresden, Hohe Straße
6, 01069 Dresden, Germany
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Qiang-bing W, Mei-rong C, Zhou F. PROGRESS ON SURFACE GRAFTED POLYMER BRUSHES FOR BIOMIMETIC LUBRICATION. ACTA POLYM SIN 2012. [DOI: 10.3724/sp.j.1105.2012.12127] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Nguyen TD, Carrillo JMY, Dobrynin AV, Brown WM. A Case Study of Truncated Electrostatics for Simulation of Polyelectrolyte Brushes on GPU Accelerators. J Chem Theory Comput 2012; 9:73-83. [DOI: 10.1021/ct300718x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Trung Dac Nguyen
- National Center
for Computational
Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831,
United States
| | - Jan-Michael Y. Carrillo
- Polymer Program,
Institute of
Materials Science and Department of Physics, University of Connecticut,
Storrs, Connecticut 06269, United States
| | - Andrey V. Dobrynin
- Polymer Program,
Institute of
Materials Science and Department of Physics, University of Connecticut,
Storrs, Connecticut 06269, United States
| | - W. Michael Brown
- National Center
for Computational
Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831,
United States
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Carrillo JMY, Brown WM, Dobrynin AV. Explicit Solvent Simulations of Friction between Brush Layers of Charged and Neutral Bottle-Brush Macromolecules. Macromolecules 2012. [DOI: 10.1021/ma3015849] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jan-Michael Y. Carrillo
- Polymer Program, Institute of
Materials Science and Department of Physics, University of Connecticut, Storrs, Connecticut 06269, United States
| | - W. Michael Brown
- Scientific Computing Department,
National Center for Computational Sciences, Oak Ridge National Laboratories, Oak Ridge, Tennessee 37831, United
States
| | - Andrey V. Dobrynin
- Polymer Program, Institute of
Materials Science and Department of Physics, University of Connecticut, Storrs, Connecticut 06269, United States
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Erk KA, Martin JD, Hu YT, Shull KR. Extreme strain localization and sliding friction in physically associating polymer gels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:4472-4478. [PMID: 22300309 DOI: 10.1021/la204592r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Model physically associating gels deformed in shear over a wide range of reduced rates displayed evidence of strain localization. The nonlinear stress responses and inhomogeneous velocity profiles observed during shear rheometry coupled with particle tracking velocimetry were associated with the occurrence of rate-dependent banding and fracture-like responses in the gel. Scaling law analysis from traditional sliding friction studies suggests that, at the molecular level, deformation is confined to a shear zone with thickness comparable to the mesh size of the gel, the smallest structurally relevant length scale in the gel.
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Affiliation(s)
- Kendra A Erk
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
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