Penetration kinetics into a previously adsorbed polymer layer

We describe a study of the time evolution of the infrared bound fraction as a polymer penetrates into a previously adsorbed layer. The system is a near-theta system, poly(methyl-methacrylate) (PMMA) in carbon tetrachloride (CCL₄). The following conclusions emerged: The mass turnover between the adsorbed state and free solution was minimal (<5%) over periods of hours; The bound fraction of the invading chains increased systematically with time elapsed, suggesting that the invading chains undergo a spreading process; The kinetics of the spreading process did not depend on the molecular weight of the invading chains, which suggests that penetration into the adsorbed layer was not rate-determining; Desorption of previously-adsorbed chains therefore appears to the rate-determining kinetic event in the present system.