Conformational Studies of Covalently Grafted Poly(ethylene glycol) on Modified Solid Matrices Using X-ray Photoelectron Spectroscopy

Amine functionalized poly(ethylene glycols) (PEGs) with molecular weights 2000 and 4000 Da were covalently grafted onto carboxy modified hydrophilic Sephadex derivatives and hydrophobic polystyrene derivatives using anhydrous amine conjugation methods. Varying PEG surface concentration and layer thickness were achieved by controlling the reaction parameters and were analyzed by X-ray photoelectron spectroscopy (XPS). C-O intensities obtained from high resolution C Is scans were correlated using the standard overlay model to study the grafting kinetics as well as conformational properties of grafted polymer chains. A detailed and systematic comparison of PEG layer thickness and distance between grafted chains with the Flory radius of surface grafted PEG resulted in valuable information regarding conformational behavior of the polymer. The influence of the nature of the solid matrix on grafting kinetics and conformational properties of the grafted polymer chain was also established from the XPS results.