Novel cationic polymers are provided by reaction of high molecular weight polymers and copolymers of acrylamide with an alkyl epoxide compound such as glycidyldialkylamine or glycidyltrialkylammonium salt to form polymer chain units containing e.g. pendant (N-2-hydroxypropyl) dialkylamine groups of their trialkylammonium salts. Processes for making the graft copolymers are provided in which the reaction is carried out while maintaining the reaction mixture in gel form by swelling the starting solid polymer with a solvent mixture.The reaction may be carried out in a homogeneous reaction environment or in a heterogeneous reaction environment by dispersing the starting solid polymer in an inert liquid that is a non-solvent for both the polymer and the salt. The polymeric products of the reaction may be hardened with a suitable liquid, such as isopropanol, to a solid particulate material.