Kinetics and multilayering in the adsorption of polyelectrolytes to a charged surface

The kinetics of radiolabeled poly(styrene sulfonate) adsorbing at a positively-charged surface were determined using a surface-charged plastic scintillator as substrate. In situ measurements indicate diffusion-limited adsorption with the final adsorbance dependent on the solution concentration of polyelectrolyte. An absence of self-exchange of unlabeled for labeled polymer suggests a thermodynamically irreversible process, at least for highly-charged polymers on highly-charged surfaces in the weak screening limit. Charge compensation of sulfonate was determined by displacement of labeled calcium (Ca-45(2+)) probe ions. Compensation is complete for surface sites and only partial for interior sulfonates. The use of radiometric techniques facilitates studies of polyelectrolyte multilayer formation.