Europhys. Lett.
Volume 75, Number 3, August 2006
Page(s) 427 - 433
Section Atomic and molecular physics
Published online 28 June 2006
Europhys. Lett., 75 (3), pp. 427-433 (2006)
DOI: 10.1209/epl/i2006-10121-x

Strongly charged polymer brushes

B. O'Shaughnessy1 and Q. Yang2

1  Department of Chemical Engineering, Columbia University New York, NY10027, USA
2  Department of Physics, Columbia University - New York, NY10027, USA

received 22 May 2006; accepted in final form 6 June 2006
published online 28 June 2006

We have established phase diagrams for strongly charged polymer brushes as a function of salt concentration $n_{\rm s}$, chain grafting density and polymer backbone charge density. We show these are qualitatively different to the previously calculated weakly charged phase diagrams due to electrostatic stiffening and counterion condensation effects, the hallmarks of highly charged polymers such as DNA. Saturated phases arise where chains are locally or globally fully stretched. We show the salt dependence of brush height H depends on the form of the persistence length $l_{\rm p}$. In good agreement with experiment, we find $H\sim\ {n}_{\rm s}^{-1/3}$ at higher salt concentrations if a linear relation between $l_{\rm p}$ and Debye length is assumed.

36.20.Ey - Conformation (statistics and dynamics).
61.20.Qg - Structure of associated liquids: electrolytes, molten salts, etc.
61.25.Hq - Macromolecular and polymer solutions; polymer melts, swelling.

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