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Taylor NM, Pilkington GA, Snow T, Dowding PJ, Cattoz BN, Schwarz AD, Bikondoa O, Vincent B, Briscoe WH. Surface forces and friction between Langmuir-Blodgett polymer layers in a nonpolar solvent. J Colloid Interface Sci 2024; 653:1432-1443. [PMID: 37804612 DOI: 10.1016/j.jcis.2023.09.146] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 08/28/2023] [Accepted: 09/24/2023] [Indexed: 10/09/2023]
Abstract
Optimization of boundary lubrication by tuning the confined molecular structures formed by surface-active additives such as surfactants and polymers is of key importance to improving energy efficiency in mechanical processes. Here, using the surface forces apparatus (SFA), we have directly measured the normal and shear forces between surface layers of a functionalised olefin copolymer (FOCP) in n-dodecane, deposited onto mica using the Langmuir-Blodgett (LB) technique. The FOCP has an olefin backbone decorated with a statistical distribution of polar-aromatic groups, with a structure that we term as "centipede". The effect of lateral confinement, characterised by the surface pressure, Πdep, at the air-water interface at which the LB films are transferred, was examined. Normal force profiles revealed that the thickness of the LB films increased significantly with Πdep, with the film thickness (t > 20 nm) inferring a multi-layered film structure, consistent with the interfacial characterisation results from synchrotron X-ray reflectivity (XRR) measurements. The coefficient of friction, µ, between the LB films spanned two orders of magnitude from superlubricity (µ ∼ 0.002) to much higher friction (µ > 0.1) depending nonlinearly on Πdep, with the lowest friction observed at the intermediate Πdep. Molecular arrangement upon LB compression leads to the multilayer film with a structure akin to an interfacial gel, with transient crosslinking facilitated by the intra- and inter-molecular interactions between the functional groups. We attribute the differences in frictional behaviour to the different prevalence of the FOCP functional groups at the lubricating interface, which depends sensitively on the degree of compression at the air-water interface prior to the LB deposition. The LB films remain intact after repeated compression (up to pressures of 10 MPa) and shear cycles, indicating strong surface anchorage and structural robustness as a load-bearing and shear-mediating boundary layer. These unprecedented results from the friction measurements between LB films of a statistical copolymer in oil point towards new strategies for tailoring macromolecular architecture for mediating efficient energy dissipation in oil-based tribological applications.
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Affiliation(s)
- Nicholas M Taylor
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Georgia A Pilkington
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Tim Snow
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Peter J Dowding
- Infineum UK Ltd, Milton Hill Business and Technology Centre, Abingdon, Oxon OX13 6BB, UK
| | - Beatrice N Cattoz
- Infineum UK Ltd, Milton Hill Business and Technology Centre, Abingdon, Oxon OX13 6BB, UK
| | - Andrew D Schwarz
- Infineum UK Ltd, Milton Hill Business and Technology Centre, Abingdon, Oxon OX13 6BB, UK
| | - Oier Bikondoa
- XMaS, The UK CRG Beamline, European Synchrotron Radiation Facility (ESRF), 71 Avenue des Martyrs, 38043 Grenoble, France; Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Brian Vincent
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Wuge H Briscoe
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
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Li M, Zhuang B, Yu J. Functional Zwitterionic Polymers on Surface: Structures and Applications. Chem Asian J 2020; 15:2060-2075. [DOI: 10.1002/asia.202000547] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 05/29/2020] [Indexed: 12/31/2022]
Affiliation(s)
- Minglun Li
- School of Materials Science and EngineeringNanyang Technological University Singapore 639798 Singapore
| | - Bilin Zhuang
- Division of ScienceYale-NUS College Singapore 138527 Singapore
| | - Jing Yu
- School of Materials Science and EngineeringNanyang Technological University Singapore 639798 Singapore
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Zhang X, Gong C, Akakuru OU, Su Z, Wu A, Wei G. The design and biomedical applications of self-assembled two-dimensional organic biomaterials. Chem Soc Rev 2019; 48:5564-5595. [DOI: 10.1039/c8cs01003j] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Self-assembling 2D organic biomaterials exhibit versatile abilities for structural and functional tailoring, as well as high potential for biomedical applications.
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Affiliation(s)
- Xiaoyuan Zhang
- State Key Laboratory of Chemical Resource Engineering
- Beijing University of Chemical Technology
- China
- Faculty of Physics and Astronomy
- University of Jena
| | - Coucong Gong
- Faculty of Production Engineering
- University of Bremen
- Bremen
- Germany
| | - Ozioma Udochukwu Akakuru
- Cixi Institute of Biomedical Engineering
- CAS Key Laboratory of Magnetic Materials and Devices, & Key Laboratory of Additive Manufacturing Materials of Zhejiang Province
- Ningbo Institute of Materials Technology and Engineering
- Chinese Academy of Sciences
- Ningbo
| | - Zhiqiang Su
- State Key Laboratory of Chemical Resource Engineering
- Beijing University of Chemical Technology
- China
| | - Aiguo Wu
- Cixi Institute of Biomedical Engineering
- CAS Key Laboratory of Magnetic Materials and Devices, & Key Laboratory of Additive Manufacturing Materials of Zhejiang Province
- Ningbo Institute of Materials Technology and Engineering
- Chinese Academy of Sciences
- Ningbo
| | - Gang Wei
- Faculty of Production Engineering
- University of Bremen
- Bremen
- Germany
- Cixi Institute of Biomedical Engineering
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