Rates of adsorption and desorption of polystyrene on chrome surface

The rate of adsorption of polystyrene from cyclohexane solution on chrome ferrotype plates was studied for a concentration range of 10^-1 to 10^-4 mg/ml. Two molecular weight fractions of polymers, 76,000 and 38,100, were prepared by the anionic polymerization of styrene tagged with tritium, and a radiotracer technique was used to measure directly the amount of polymer adsorbed on the surface. The rate of adsorption is very dependent on the concentration of the polymer solution, and times varying from minutes to several hours were required before maximum adsorption occurred for the concentration range studied. The rate of desorption is strongly dependent on the adsorbance; it was hypothesized that this is due to the number of attachments per molecule also varying with adsorbance. The conformation of the adsorbed molecule as indicated by these results and those determined by the measurement of the thickness of the adsorbed layer by ellipsometry is discussed.