Kettenübertragung durch tetrabromkohlenstoff bei der polymerisation von styrol und von vinylacetat

The constant of chain transfer to carbon tetrabromide in the polymerization of styrene has been redetermined by directly measuring the consumption of the chain transfer agent using a GC-technique and simultaneously evaluating the conversion of monomer to polymer. Values of 250 (at 60°C) and 185 (at 95°C) have been obtained by this method. These values agree in order of magnitude with those recently obtained by Thomson and Walters from the determination of polymer molecular weights and, accordingly, exceed the values previously reported by approximately two powers of ten. An analysis of the limiting viscosity numbers of the polymers prepared in presence of carbon tetrabromide shows an excellent agreement with these new high values of the chain transfer constant of carbon tetrabromide. For the constant of chain transfer to carbon tetrabromide in the polymerization of vinyl acetate a value of 6·10³ has been obtained at 60°C, which again is two to three orders of magnitude higher than those values given previously.