The deoxy-di-n-propylamino (II) and deoxy-thio (V) derivatives of ethyl cellulose have been prepared. Catalyzed polymerization of acrylonitrile in the presence of (II) results in chain transfer between the polyacrylonitrile radical and the tertiary amino group, with subsequent graft polymerization. A copolymer of ca. 40% polyacrylonitrile grafted on ethyl cellulose was isolated by a combination of fractional precipitation and selective extraction. Polymerization of styrene in presence of (V) results in chain transfer between the polystyrene radical and the thiol groups, with subsequent graft polymerization. Fractional precipitation of the product yielded a fraction whose ethoxyl analysis corresponds to a copolymer of 86% polystyrene grafted on ethyl cellulose.