Strongly charged polymer brushes

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: 6 June 2006

Abstract

We have established phase diagrams for strongly charged polymer brushes as a function of salt concentration n_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_p. In good agreement with experiment, we find at higher salt concentrations if a linear relation between l_p and Debye length is assumed.