copolymers of dimethylaminopropyl methacrylamide and hydroxyethyl methacrylate having residual monomer levels of & lt ; 2000 ppm and & lt ; 500 ppm , respectively , are made by copolymerizing the monomers in a predetermined weight ratio in an aqueous - alcoholic solvent of defined composition . substrates coated with these copolymers are capable of absorbing the solvents , e . g . water or organic solvents , of digital printing inks rapidly with dry times of & lt ; 1 min .