The copolymerization of ethylene (III) and maleic anhydride (II) in ethylbenzene (I) by means of benzoyl peroxide (IV) at 70 C gives an ethylene/maleic anhydride copolymer (V), which is ammoniated by treating with liquid ammonia in acetone yielding the ammoniated ethylene/maleic acid copolymer (VI). Finally, this product is imidated partially by heating in refluxing xylene.