AbstractAlternating copolymers of phenylvinyl ethyl ether (I) and phenylvinyl sec‐butyl ether (II) with maleic anhydride (MAn) were prepared in bulk or in benzene solution by high‐energy irradiation at dose rates of 42, 160, and 540 Gy/h, respectively. The overall energies of activation in copolymerization ofIandIIwith MAn were 15.5 and 18.8 kJ/mol, respectively. The reaction proceeds by the free‐radical mechanism and was found to be largely dependent on the bulkiness of the alkyl group. In the copolymerization ofIand MAn, the molecular weight increases with conversion. By applying the model described by Shirota and co‐workers, it was established that participation of charge‐transfer‐complex monomers increases with the increase of the total monomer concentration and with the bulkiness of the alkyl group in electron do