ADSORPTION OF THIOL-CONTAINING COPOLYMERS ONTO GOLD

Polystyrene and poly(styrenesulfonate) copolymers bearing (mercaptomet hyl)styrene units have been synthesized via an amidinothio intermediat e which allows for quantitative hydrolysis to the thiol. The kinetics of adsorption of these polymers to gold has been determined in situ us ing the quartz crystal microbalance. The introduction of a few percent of thiol groups causes polystyrene to adsorb to gold from a good solv ent (THF). Poly(styrenesulfonate) can also be induced to adsorb at a n egatively charged (repulsive) gold/water interface when heavily loaded with (mercaptomethyl)styrene. Copolymers adsorb relatively rapidly, a ttaining stable surface coverages within 1 h. Steady-state adsorbance for copolymers of wide molecular-weight distribution is taken as indir ect evidence for adsorption in the nonequilibrium regime. Electron spe ctroscopy of adsorbed poly(styrenesulfonate) copolymers suggests that sulfonate groups are expelled from the metal/polymer interface. The ki netics of octadecanethiol chemisorbing to gold was studied to provide a well-characterized, small-molecule comparison.