THE ADSORPTION OF POLYMERS ONTO MICA: DIRECT MEASUREMENTS USING MICROBALANCE AND REFRACTIVE INDEX TECHNIQUES

Abstract

This chapter describes the determination of the kinetics of adsorption, and the adsorption isotherms of polystyrene adsorbing onto mica from cyclohexane at the θ-temperature (34.5±0.5°C) using the microbalance and refractive index techniques. The adsorption of both PS3 and PS4 from cyclohexane at the θ-temperature onto freshly cleaved mica is rapid, and the plateau value of T at all concentrations is reached at the first measured point on the adsorption v s . time curve. The extent of desorption of PS3 and PS4 is negligible over periods of up to 17 hours. The adsorption of probe beam deflection onto freshly cleaved mica in good solvent conditions is also rapid and appears to be quasi-irreversible. The adsorption isotherm plateau values for PS3 and PS4 are comparable with those determined in ellipsometric and radiometric studies of polystyrene adsorption onto various plane surfaces from cyclohexane under θ-conditions. The adsorbance of PS1 onto the mica surfaces, as determined from refractive index measurements, following 10 hours of incubation is the equilibrium value for the conditions of that study. The adsorbance of polyethylene oxide from aqueous solution onto mica surfaces has been measured using the refractive index approach. The results indicate a considerably higher adsorbance than previously measured for PEO adsorbing onto colloidal silica particles.