Adsorption of Ethylene–Vinyl Acetate Copolymer on Silica Surface

Abstract

Adsorption of ethylene–vinyl acetate copolymers (vinyl acetate content (mol%) ca. 60) onto a nonporous silica (Aerosil 130) from trichloroethylene solutions at 25°C was studied by IR spectroscopy and differential refractometry. The observed IR frequency shift of the silanol groups was attributed to hydrogen bonding between ester carbonyl groups in the copolymer and the silanol groups. The adsorbance, A, was determined by a differential refractometer, while the fraction of silanol groups occupied, θ, and the fraction of the adsorbed ester carbonyl groups, p, were determined by IR spectroscopy. The three important quantities A, θ, and p reached plateau values at extremely low polymer concentrations. The value of A for the copolymer in the plateau region somewhat increased with increasing molecular weight. The plateau values of both p and θ were nearly independent of molecular weight.