The suppression of electro-osmotic flow (EOF) through the use of a dynamically adsorbed polymer coating is a widely used technique in microfluidic devices. Recent experimental evidence has suggested that the most effective coatings are those which are only weakly adsorbed to the surface. We report molecular dynamics simulation results which show that the optimal adsorption strength for the suppression of EOF is around the transition for adsorption of the polymer. Our results should help to guide the design of novel polymer coatings for improved quenching of EOF.