Polymerization of styrene in presence of tetramethylthiuramdisulphide

Abstract During the polymerization of styrene (also of methylmethacrylate) in the presence of tetra-methylthiuramdisulphide, there is deviation from the simple reaction scheme. This deviation is explained by the participation of RS . radicals (formed by thermal decomposition of TMTD and by transfer of P . radicals to TMTD) in termination reactions. The total polymerization rate is then well expressed by derived relation (1); it was possible to determine the complex constants B * and C * (for styrene C*→0). The study of the influence of [TMTD] on the molecular weight of polystyrene (determined visco-metrically) enables evaluation of transfer constants C T and of rate constants k 4 by means of the relation (4). The determined values of activation energy E 4 = 11·5 ± 1 kcal. mol −1 and E B* = 6·3 ± 1 kcal, mol −1 lead to E ′ 1 = 5·2 ± 2 kcal × mol −1 (for the reaction R S · + M → k 1 P · ) with the assumption that E 3 = E ′ 3 . The activation energy of initiation E i = 24 ± 2 kcal. mol −1 (the initiation rates R i were calculated from the experimental values of R p for [TMTD] approaching zero) is in good agreement with the activation energy for the consumption of [TMTD] during the vulcanization of rubber.