Interfacial Friction and Adhesion of Polymer Brushes

Lucas J. T. Landherr, Claude Cohen, Praveen Agarwal, Lynden A. Archer

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

A 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.
Original languageEnglish (US)
Pages (from-to)9387-9395
Number of pages9
JournalLangmuir
Volume27
Issue number15
DOIs
StatePublished - Aug 2 2011
Externally publishedYes

Fingerprint

Dive into the research topics of 'Interfacial Friction and Adhesion of Polymer Brushes'. Together they form a unique fingerprint.

Cite this