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Phys. Rev. Lett. 91, 115503 (2003) [4 pages]

Sliding Friction with Polymer Brushes

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Rafael Tadmor*, Joanna Janik†, and Jacob Klein‡
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
and Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, United Kingdom

Lewis J. Fetters§
Exxon Research and Engineering Corporation, Annandale, New Jersey 08801, USA

Received 2 May 2002; published 9 September 2003

Using high-resolution shear force measurements, we examine in detail the frictional drag between rubbing surfaces bearing end-tethered polymeric surfactants (brushes). The drag attains a maximum on initial motion, attributed to elastic stretching of the chains, which falls by a cascade of relaxations to a value characteristic of kinetic friction. This has a very weak velocity dependence, attributed to chain moieties dragging within a self-regulating, mutual interpenetration zone. When sliding stops, the shear stress across the polymer layers decays logarithmically with time, consistent with the relaxation of a network of dangling ends.

© 2003 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.91.115503
DOI:
10.1103/PhysRevLett.91.115503
PACS:
81.40.Pq, 79.60.Dp, 83.10.Gr

*Present address: Department of Chemical Engineering, Lamar University, P.O. Box 10053, Beaumont, TX 77710, USA.

†Present address: Department of Physics, Jagelonian University, Krakow, Poland.

‡Corresponding author.

Email address: jacob.klein@chem.ox.ac.uk or jacob.klein@weizmann.ac.il

§Present address: Chemical & Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA.

 
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