Molecular dynamics studies of anchored polyelectrolytes

We study polyelectrolytes end-grafted to a surface in a model which include s counterions explicitly and treats the full long-range Coulomb interaction . For strongly charged polyelectrolytes the counterions are localized insid e the brush and electroneutrality is satisfied locally. Under these conditi ons, we find that the brush thickness is linearly proportional to the chain length and the grafting density. The counterion distribution is strongly i nhomogeneous, and counterion condensation can be observed although the Bjer rum length is smaller than the average bond length. Varying the Bjerrum len gth we find a non-monotonic behaviour of the brush height. Counterion diffu sion is anisotropic, and is enhanced at higher grafting densities. For part ially charged polyelectrolytes we obtain a crossover from quasi-neutral beh aviour to the strongly charged behaviour reported above.