KINETICS OF ADSORPTION OF LINEAR HOMOPOLYMERS ONTO FLAT SURFACES - ROUSE DYNAMICS

The dynamic properties of unentangled adsorbed polymer layers are cons idered theoretically. The kinetics of penetration of a chain in an ads orbed layer is considered as a two-step process: entry corresponding t o the attachment of the chain on the adsorbing surface and spreading o n the surface. We discuss three types of experiments, the formation of an adsorbed layer, the desorption from an adsorbed layer and the exch ange between an adsorbed layer and a bulk solution. The bottleneck for the adsorption of a new chain onto a solid wall (already covered by p olymers) is the spreading stage corresponding to creation of G contact s with the wall with a total binding energy of order of kT. The desorp tion of a preadsorbed layer in contact with pure solvent is extremely slow and only a very small fraction of the adsorbed chains is expected to desorb within the experimental time scale. The exchange between la belled adsorbed chains and unlabelled chains in solution is slower tha n the formation of a saturated layer, but much faster than the desorpt ion process. The molecular weight dependencies of the characteristic t imes of the three processes are predicted using the Rouse-Zimm dynamic s for the polymer chains.