A switchable polymer layer: Chain folding in end-charged polymer brushes

We use a self-consistent field approximation to model the configurations of end-charged homopolymer and block copolymer brushes in response to an exte rnal electric field due to charges on the grafting surface. By varying the charge density on the grafting surface, we can cause the chains either to e xtend outward, greatly increasing the brush height, or to loop back to the grafting surface. We show that such a copolymer brush can present one block at the exposed surface in the extended state and present the other block i n the retracted state. This occurs for both a solvated brush and a dry brus h. We also compare these results to those of a modified Alexander-de Gennes model for the end-charged homopolymer brush. (C) 2001 American Institute o f Physics.