Rod-like polyelectrolyte brushes with mono- and multivalent counterionsH. Fazli1, R. Golestanian1, P. L. Hansen2 and M. R. Kolahchi1
1 Institute for Advanced Studies in Basic Sciences - Zanjan 45195-1159, Iran
2 MEMPHYS-Center for Biomembrane Physics, Physics Department University of Southern Denmark - DK-5230 Odense M, Denmark
received 20 October 2005; accepted 28 November 2005
published online 16 December 2005
A model of rod-like polyelectrolyte brushes in the presence of monovalent and multivalent counterions but with no added salt is studied using Monte Carlo simulation. The average height of the brush, the histogram of rod conformations, and the counterion density profile are obtained for different values of the grafting density of the charge-neutral wall. For a domain of grafting densities, the brush height is found to be relatively insensitive to the density due to a competition between counterion condensation and inter-rod repulsion. In this regime, multivalent counterions collapse the brush in the form of linked clusters. Nematic order emerges at high grafting densities, resulting in an abrupt increase of the brush height.
82.35.Rs - Polyelectrolytes.
83.80.Xz - Liquid crystals: nematic, cholesteric, smectic, discotic, etc.
87.68.+z - Biomaterials and biological interfaces.
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