KINETICS, ISOTHERMS, AND COMPETITION IN POLYMER ADSORPTION USING THE QUARTZ-CRYSTAL MICROBALANCE

The kinetics and isotherms of adsorption of polystyrene and poly(ethyl ene oxide) at the solution/metal interface have been measured in situ using the quartz crystal microbalance. For polystyrene, cyclohexane at the theta temperature was used as the solvent and gold as the surface . Isotherms for polystyrene over the molecular weight range 10(4) to 1 0(5) were confirmed to be of the high-affinity type. The effect of sol ution viscosity on frequency measurements was considered in detail and shown to be negligible over a range of conditions. The surface displa cement of lower molecular weight polymer by higher molecular weight po lymer was shown to be rapid. Using polymers having a wide molecular we ight distribution, it was demonstrated that a limiting, stable value f or surface coverage is attained more slowly, suggesting continuous com petition for sites among molecules of different sizes. Poly(ethylene o xide) adsorbed onto gold from a good solvent, whereas polystyrene did not.