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Briscoe WH. Aqueous boundary lubrication: Molecular mechanisms, design strategy, and terra incognita. Curr Opin Colloid Interface Sci 2017. [DOI: 10.1016/j.cocis.2016.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Pilkington GA, Briscoe WH. Nanofluids mediating surface forces. Adv Colloid Interface Sci 2012; 179-182:68-84. [PMID: 22795777 DOI: 10.1016/j.cis.2012.06.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 04/13/2012] [Accepted: 06/23/2012] [Indexed: 12/28/2022]
Abstract
Fluids containing nanostructures, known as nanofluids, are increasingly found in a wide array of applications due to their unique physical properties as compared with their base fluids and larger colloidal suspensions. With several tuneable parameters such as the size, shape and surface chemistry of nanostructures, as well as numerous base fluids available, nanofluids also offer a new paradigm for mediating surface forces. Other properties such as local surface plasmon resonance and size dependent magnetism of nanostructures also present novel mechanisms for imparting tuneable surface interactions. However, our fundamental understanding, experimentally and theoretically, of how these parameters might affect surface forces remains incomplete. Here we review recent results on equilibrium and dynamic surface forces between macroscopic surfaces in nanofluids, highlighting the overriding trends in the correlation between the physical parameters that characterise nanofluids and the surface forces they mediate. We also discuss the challenges that confront existing surface force knowledge as a result of this new paradigm.
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Dunlop IE, Thomas RK, Titmus S, Osborne V, Edmondson S, Huck WTS, Klein J. Structure and collapse of a surface-grown strong polyelectrolyte brush on sapphire. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:3187-3193. [PMID: 22292571 DOI: 10.1021/la204655h] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have used neutron reflectometry to investigate the behavior of a strong polyelectrolyte brush on a sapphire substrate, grown by atom-transfer radical polymerization (ATRP) from a silane-anchored initiator layer. The initiator layer was deposited from vapor, following treatment of the substrate with an Ar/H(2)O plasma to improve surface reactivity. The deposition process was characterized using X-ray reflectometry, indicating the formation of a complete, cross-linked layer. The brush was grown from the monomer [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), which carries a strong positive charge. The neutron reflectivity profile of the swollen brush in pure water (D(2)O) showed that it adopted a two-region structure, consisting of a dense surface region ∼100 Å thick, in combination with a diffuse brush region extending to around 1000 Å from the surface. The existence of the diffuse brush region may be attributed to electrostatic repulsion from the positively charged surface region, while the surface region itself most probably forms due to polyelectrolyte adsorption to the hydrophobic initiator layer. The importance of electrostatic interactions in maintaining the brush region is confirmed by measurements at high (1 M) added 1:1 electrolyte, which show a substantial transfer of polymer from the brush to the surface region, together with a strong reduction in brush height. On addition of 10(-4) M oppositely charged surfactant (sodium dodecyl sulfate), the brush undergoes a dramatic collapse, forming a single dense layer about 200 Å in thickness, which may be attributed to the neutralization of the monomers by adsorbed dodecyl sulfate ions in combination with hydrophobic interactions between these dodecyl chains. Subsequent increases in surfactant concentration result in slow increases in brush height, which may be caused by stiffening of the polyelectrolyte chains due to further dodecyl sulfate adsorption.
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Affiliation(s)
- Iain E Dunlop
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
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A 2H nuclear magnetic resonance study of the state of water in neat silica and zwitterionic stationary phases and its influence on the chromatographic retention characteristics in hydrophilic interaction high-performance liquid chromatography. J Chromatogr A 2011; 1218:6630-8. [DOI: 10.1016/j.chroma.2011.04.056] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 04/11/2011] [Accepted: 04/20/2011] [Indexed: 11/16/2022]
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Drechsler A, Synytska A, Uhlmann P, Elmahdy MM, Stamm M, Kremer F. Interaction forces between microsized silica particles and weak polyelectrolyte brushes at varying pH and salt concentration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:6400-6410. [PMID: 20038115 DOI: 10.1021/la904103z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The AFM colloidal probe technique was used to measure the interaction between microsized silica spheres and annealed polyelectrolyte brushes made of poly(acrylic acid) (PAA) and poly(2-vinyl pyridine) (P2VP) in KCl solutions of various pH values and salt concentrations. The interaction energy showed a distance dependence that was affected strongly by the swelling and the electric properties of the brushes. Between PAA brushes and silica particles, a repulsive interaction has been observed for all pH values and salt concentrations reflecting the swelling of the brush with varying pH value and the transition from osmotic to salted brush regime with increasing KCl concentration. Force measurements between P2VP brushes and silica particles revealed a much more complex behavior: a steric repulsion by the swollen brush at low pH values, a complex interplay of attractive and repulsive forces at intermediate pH values and a short-ranged attraction between the collapsed brush and the silica particle at basic pH values and high salt concentrations. The results are interpreted in comparison with the Alexander de Gennes model and zeta potential and ellipsometric measurements.
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Affiliation(s)
- Astrid Drechsler
- Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden, Germany.
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Malham IB, Bureau L. Density effects on collapse, compression, and adhesion of thermoresponsive polymer brushes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:4762-4768. [PMID: 19961208 DOI: 10.1021/la9035387] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We probe, using the surface forces apparatus, the thermal response of poly(N-isopropylacrylamide) (PNIPAM) brushes of various grafting densities, grown from plasma-activated mica by means of surface-initiated polymerization. We thus show that dense thermoresponsive brushes collapse gradually as temperature is increased and that grafting density greatly affects their ability to swell: the swelling ratio of the brushes, which characterizes the thickness variation between the swollen and the collapsed state, is found to decrease from approximately 7 to approximately 3 as the number of grafted chains per unit area increases. Such a result, obtained with an unprecedented resolution in grafting density, provides qualitative support to calculations by Mendez et al. [Macromolecules 2005, 38, 174]. We further show that, in contrast to swelling, adhesion between two PNIPAM brushes appears to be rather insensitive to their molecular structure.
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Affiliation(s)
- Ibrahim B Malham
- Institut des Nanosciences de Paris, UMR 7588 CNRS-Université Paris 6, 140 rue de Lourmel, 75015 Paris, France
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Dunlop IE, Briscoe WH, Titmuss S, Jacobs RMJ, Osborne VL, Edmondson S, Huck WTS, Klein J. Direct Measurement of Normal and Shear Forces between Surface-Grown Polyelectrolyte Layers. J Phys Chem B 2009; 113:3947-56. [DOI: 10.1021/jp807190z] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Iain E. Dunlop
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Wuge H. Briscoe
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Simon Titmuss
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Robert M. J. Jacobs
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Vicky L. Osborne
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Steve Edmondson
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Wilhelm T. S. Huck
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
| | - Jacob Klein
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, U.K., Melville Laboratory for Polymer Synthesis, University Chemistry Laboratory, Lensfield Road, Cambridge, CB2 1EW, U.K., and Department of Materials and Interfaces, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel
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Hiotelis I, Koutsioubas AG, Spiliopoulos N, Anastassopoulos DL, Vradis AA, Toprakcioglu C, Menelle A, Sakellariou G, Hadjichristidis N. Neutron Reflectivity and Computer Simulation Studies of Self-Assembled Brushes Formed by Centrally Adsorbed Star Polymers. Macromolecules 2008. [DOI: 10.1021/ma702749z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ioannis Hiotelis
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Alexandros G. Koutsioubas
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Nikolaos Spiliopoulos
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Dimitris L. Anastassopoulos
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Alexandros A. Vradis
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Chris Toprakcioglu
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Alain Menelle
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - George Sakellariou
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
| | - Nikos Hadjichristidis
- Physics Department, University of Patras, Patras 26500, Greece 26500; Laboratoire Leon Brillouin, CEA SACLAY, 91191 Gif-sur-Yvette Cedex, France; and Chemistry Department, University of Athens, Panepistimioupoli Zografou 15771, Greece
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Park MK, Sakellariou G, Pispas S, Hadjichristidis N, Advincula R. On the quantitative adsorption behavior of multi-zwitterionic end-functionalized polymers onto gold surfaces. Colloids Surf A Physicochem Eng Asp 2008. [DOI: 10.1016/j.colsurfa.2008.05.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Lego B, Skene WG, Giasson S. Unprecedented covalently attached ATRP initiator onto OH-functionalized mica surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:379-382. [PMID: 18076200 DOI: 10.1021/la703051b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Mica substrates were activated by a plasma method leading to OH-functionalized surfaces to which an atom transfer radical polymerization (ATRP) radical initiator was covalently bound using standard siloxane protocols. The unprecedented covalently immobilized initiator underwent radical polymerization with tert-butyl acrylate, yielding for the first time end-grafted polymer brushes that are covalently linked to mica. The initiator grafting on the mica substrate was confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS), while the change in the water contact angle of the OH-activated mica surface was used to follow the change in surface coverage of the initiator on the surface. The polymer brush and initiator film thicknesses relative to the virgin mica were confirmed by atomic force microscopy (AFM). This was done by comparing the atomic step-height difference between a protected area of freshly cleaved mica and a zone exposed to plasma activation, initiator immobilization, and then ATRP.
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Affiliation(s)
- Béatrice Lego
- Department of Chemistry, Université de Montréal, C.P. 6128, succursale Centre-Ville, Montréal, Québec, Canada H3C 3J7
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