Collapse of polyelectrolyte brushes in electric fields
Department of Materials and Interfaces, Weizmann Institute of Science - Rehovot 76100, Israel
2 Materials Research Laboratory, University of California at Santa Barbara - Santa Barbara, CA 93106, USA
3 Department of Physics, Korea Advanced Institute of Science and Technology (KAIST) - Daejeon 305701, Korea
Accepted: 1 July 2011
We predict the collapse of a polyelectrolyte brush grafted on an electrode that is induced by applied electric fields for the limiting cases of low and high salt concentrations. The polyelectrolyte brush collapses locally to screen the charges induced on the electrodes. For low salt concentrations, the height of the polyelectrolyte brush decreases steeply with increasing the voltage between the electrodes because the number of counterions expelled from the brush increases exponentially. However, when the system is in equilibrium with monovalent salts at high concentrations, the brush height decreases almost linearly with increasing the voltage instead of the steep collapse. This is because the voltage drop mainly occurs over the diffuse double layer associated with the distant electrode.
PACS: 82.35.Rs – Polyelectrolytes / 68.47.Pe – Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
© EPLA, 2011