KAUST Grant NumberKUS-C1-018-02
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AbstractA bead-probe lateral force microscopy (LFM) technique is used to characterize the interfacial friction and adhesion properties of polymer brushes. Our measurements attempt to relate the physical structure and chemical characteristics of the brush to their properties as thin-film, tethered lubricants. Brushes are synthesized at several chain lengths and surface coverages from polymer chains of polydimethylsiloxane (PDMS), polystyrene (PS), and a poly(propylene glycol)-poly(ethylene glycol) block copolymer (PPG/PEG). At high surface coverage, PDMS brushes manifest friction coefficients (COFs) that are among the lowest recorded for a dry lubricant film (μ ≈ 0.0024) and close to 1 order of magnitude lower than the COF of a bare silicon surface. Brushes synthesized from higher molar mass chains exhibit higher friction forces than those created using lower molar mass polymers. Increased grafting density of chains in the brush significantly reduces the COF by creating a uniform surface of stretched chains with a decreased surface viscosity. Brushes with lower surface tension and interfacial shear stresses manifest the lowest COF. In particular, PDMS chains exhibit COFs lower than PS by a factor of 3.7 and lower than PPG/PEG by a factor of 4.7. A scaling analysis conducted on the surface coverage (δ) in relation to the fraction (ε) of the friction force developing from adhesion predicts a universal relation ε ∼ δ4/3, which is supported by our experimental data. © 2011 American Chemical Society.
CitationLandherr LJT, Cohen C, Agarwal P, Archer LA (2011) Interfacial Friction and Adhesion of Polymer Brushes. Langmuir 27: 9387–9395. Available: http://dx.doi.org/10.1021/la201396m.
SponsorsSupport from Award No. KUS-C1-018-02 made by King Abdullah University of Science and Technology (KAUST) and from the National Science Foundation Polymers Program (Grant DMR- 0705565) is gratefully acknowledged. The AFM sliding friction measurements were performed using facilities of the Cornell Center for Materials Research (CCMR), a Materials Research Science and Engineering Center of the National Science Foundation (DMR-0520404).
PublisherAmerican Chemical Society (ACS)
CollectionsPublications Acknowledging KAUST Support
- Effect of pendent chains on the interfacial properties of thin polydimethylsiloxane (PDMS) networks.
- Authors: Landherr LJ, Cohen C, Archer LA
- Issue date: 2011 May 17
- Interfacial friction and adhesion of cross-linked polymer thin films swollen with linear chains.
- Authors: Zhang Q, Archer LA
- Issue date: 2007 Jul 3
- Friction and normal interaction forces between irreversibly attached weakly charged polymer brushes.
- Authors: Liberelle B, Giasson S
- Issue date: 2008 Feb 19
- Exploring lubrication regimes at the nanoscale: nanotribological characterization of silica and polymer brushes in viscous solvents.
- Authors: Nalam PC, Ramakrishna SN, Espinosa-Marzal RM, Spencer ND
- Issue date: 2013 Aug 13
- Adhesion and friction properties of polymer brushes: fluoro versus nonfluoro polymer brushes at varying thickness.
- Authors: Bhairamadgi NS, Pujari SP, Leermakers FA, van Rijn CJ, Zuilhof H
- Issue date: 2014 Mar 4