Volume 82, Number 4, May 2008
Article Number 46001
Number of page(s) 6
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 25 April 2008
EPL, 82 (2008) 46001
DOI: 10.1209/0295-5075/82/46001

Interfacial instability of charged$\hbox{--}$end-group polymer brushes

Y. Tsori1, D. Andelman2 and J.-F. Joanny3

1  Department of Chemical Engineering, Ben-Gurion University of the Negev - P.O. Box 653, 84105 Beer-Sheva, Israel
2  Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University - Ramat Aviv, Tel Aviv 69978, Israel
3  Physico Chimie Curie, Institut CurieCentre de Recherche (CNRS UMR 168, Université Paris IV) 26 rue d'Ulm, F-75248, Paris Cedex 05, France, EU

received 21 January 2008; accepted in final form 25 March 2008; published May 2008
published online 25 April 2008

We consider a polymer brush grafted to a surface (acting as an electrode) and bearing a charged group at its free end. Using a second distant electrode, the brush is subject to a constant electric field. Based on a coarse-grained continuum model, we calculate the average brush height and find that the brush can stretch or compress depending on the applied field and charge end-group. We further look at an undulation mode of the flat polymer brush and find that the electrostatic energy scales linearly with the undulation wave number, q. Competition with surface tension, scaling as q2, tends to stabilize a lateral q-mode of the polymer brush with a well-defined wave length. This wavelength depends on the brush height, surface separation, and several system parameters.

61.25.H- - Macromolecular and polymers solutions; polymer melts.
41.20.Cv - Electrostatics; Poisson and Laplace equations, boundary-value problems.

© EPLA 2008