POLY(ETHYLENE GLYCOL) GRAFTED TO QUARTZ - ANALYSIS IN TERMS OF A SITE-DISSOCIATION MODEL OF ELECTROOSMOTIC FLUID-FLOW

Poly(ethylene glycol) coatings are known to control a variety of surfa ce phenomena including nonspecific protein adsorption, wetting, and el ectrokinetic effects. These and other properties make such coatings us eful for biocompatible materials and in improving the efficiency of an alytical and preparative separations where analyte-surface interaction s play a role. In the present study terminally activated poly(ethylene glycol) derivatives were grafted onto quartz functionally activated w ith (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane , or poly(ethylenimine). Grafts and activated surfaces were electro-ki netically characterized by measuring the pH dependence of induced elec troosmotic fluid flow. A site-dissociation model of electroosmotic flu id flow based on the Smoluchowski equation, the Gouy-Chapman theory of the electrical double layer, and exact solutions to the Poisson-Boltz mann equation is presented in order to relate electroosmosis to the ch emistry of the surface. Results include indications of relative coatin g stability and estimates of grafting density as well as effective coa ting thickness.