| Abstract: | Dimethylaniline (DMA) induces chain transfer in the zinc bromide-complexed donor–acceptor polymerizations of styrene–acrylonitrile to form alternating copolymers. The Mayo plots are linear, but the rates decrease with increase in DMA and degradative chain transfer occurs. Although conventional free-radical transfer agents have negligible effect on the rates or molecular weights, a twentyfold reduction of molecular weight is obtained with DMA. Spectroscopic data indicate the formation of an equimolar complex of DMA and ZnBr2, but the lowering of molecular weight is not attributable to the reduction of the effective ZnBr2, concentration. A possible mechanism involving a competition between [ZnBr2(DMA)2] and [ZnBr2,DMA,AN] is suggested. |
