Issue |
Europhys. Lett.
Volume 54, Number 1, April 2001
|
|
---|---|---|
Page(s) | 65 - 71 | |
Section | Condensed matter: structure, mechanical and thermal properties | |
DOI | https://doi.org/10.1209/epl/i2001-00229-y | |
Published online | 01 December 2003 |
Self-assembled layers under flow: Stabilization by chain end exchange
Institut Charles Sadron - 6 rue Boussingault, F-67083
Strasbourg Cedex, France
Corresponding author: johner@ics.u-strasbg.fr
Received:
16
October
2000
Accepted:
29
January
2001
In previous theories of sheared grafted polymer layers, the chain
configurations are stationary. Formally, the shear stress is thus
always supported by the same chains. These models predict that the
response to the flow (in plane tension at the wall, free end
deflection) is larger than the thermodynamic fluctuations for Deborah
numbers . Here we take into account the exchange of the chain
configurations so that an individual chain on average does not support
the shear stress long enough to reach a steady-state
configuration. This effect smears out the response to flow over a
larger number of chains, those with ends within one coil radius from
the edge. The response only reaches the magnitude of the thermal
fluctuations for De=1. This corresponds in practice to shear rates
as high as several
. Recent experiments by Baker
et al. indeed show that self-assembled copolymer layers are very
stable against steady shear flow, shear-induced desorption is only
detected for
.
PACS: 61.41.+e – Polymers, elastomers, and plastics / 68.08.-p – Liquid-solid interfaces / 47.50.+d – Non-Newtonian fluid flows
© EDP Sciences, 2001
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