Abstractα‐Chloromaleic anhydride (CMA) copolymerizes spontaneously with styrene (ST) at a higher rate than maleic anhydride (MA), and α,α′ ‐dichloromaleic anhydride (DCMA) does not copolymerize, even in the presence of a radical initiator. The results obtained from the copolymerization of ST with CMA in 1,4‐dioxane in the absence of a radical initiator are as follows: the copolymerization is strongly accelerated by UV‐irradiation; the monomer reactivity ratios of ST and CMA at 60°C are 0,06 and 0,00, respectively; the over‐all activation energy of the copolymerization is 77,4 kJ · mol−1(18,5 kcal · mol−1); the maximum rate of copolymerization at a constant total monomer concentration is observed at a mole fraction of ST of 0,4 to 0,5. The rate of copolymerization at equimolar feed composition is of second order with respect to the total monomer concentration. From the results obtained here and shown in the preceding paper, it was inferred that initiating radicals for the spontaneous copolymerization are formed through a charge transfer (CT) complex b