Kinetics of adsorption of block copolymers from dilute solution

Abstract

We have studied the rate of adsorption of diblock and triblock copolymers of poly(vinyl-2-pyridine) and polystyrene from toluene solutions onto silver and gold surfaces by surface plasmon spectroscopy. The optical model used in data interpretation has been confirmed by quartz crystal microbalance and ellipsometric measurements of the absorbed films. The kinetics of adsorption are highly dependent on the concentration of the solution and on the composition of the copolymer. The presence of micelles at higher concentrations leads to a high initial rate of adsorption, but the adsorption of unimers proceeds more slowly. Micelles contribute to adsorption at a higher rate (on equal mass basis) than do unimers. At later times when the surface is mostly covered, only unimers adsorb. The rate of adsorption is far below that which would be expected for a diffusion controlled process. The adsorbed molecules do not desorb into pure solvent.