Initiation and termination mechanism in the cooligomerization of the styrene–methyl methacrylate–carbon tetrachloride system

The analysis of the endgroups of the oligomers produced in the styrene (A)–CCl₄(S) system (system I), the methyl methacrylate(B)–CCl₄ system (system II), and the styrene–methyl methacrylate–CCl₄ system (system III) was carried out in order to clarify the mechanism of the initiation, transfer, and termination. In system I, the number of Cl atoms per oligomer molecule N_Cl increases with the molar ratio of S]/A] when the molar ratio of S]/A] is below unity and is about four when the molar ratio of S]/A] is above unity, and the number of initiator fragments per oligomer molecule N_I decreases with the increase in the molar ratio of S]/A]. In system II, N_Cl is about 0.45 over a considerably wide range of the molar ratio of S]/B]. In system III, N_Cl increases and N_I decreases with the increase in the molar ratios of S]/(A] + B]) and A]/B]. From the data of N_Cl and N_I, the fraction I_CC14 of the initiation by the tri-chloromethyl radical in the overall initiation reactions and the fraction T_CC14 of the chain transfer reaction of the growing radical of styrene in all the reactions which produce the cooligomer in the system III were calculated. I_CCl3 and T_CC14 both increase with the molar ratios S]/(A] + B]) and A]/B].