This invention relates to chemical modification of polymers to impart cationic properties thereto.  More particularly it relates to chemical modification by aminoalkylation of amido groups, ##STR1## contained in the main chain of the polymer. 
Methods are constantly being sought to impart hydrophilic, cationic properties to polymeric substances for a variety of purposes.  One of the most obvious routes has been to form the polymer, at least in part, from a polymerizable, cationic monomer such as vinyl pyridine, dimethylaminoethyl methacrylate, etc.  However, few such monomers are commercially available and they usually are expensive.  The other drawback to this route is that it is not possible to modify only the surface of the polymer or the article prepared therefrom. 
Among the methods of interest to modify a polymeric material has been the reaction of ethylenimine and the like with the polymer either in solution, etc.,  to homogeneously modify it or with an article thereof to modify the surface only.  However, ethylenimine is a highly reactive chemical which under acid catalysts prefers to react with itself to form polyethylenimine rather than to react with the polymer to any significant extent.  Due to the commercial availability now of ethylenimine and propylenimine it would be desirable to have a method which utilizes ethylenimine, etc.  to impart cationic properties to polymeric materials.