Chain transfer with bromotrichloromethane in the polymerization of styrene

Abstract

Equations have been developed in an attempt to describe and correct for the effect of reactant removal on the degree of polymerization of the polymer produced in the presence of a reactive substrate and consequently on the observed value of the transfer constant. Bromotrichloromethane is suitably reactive in transfer with polystyrene radicals to allow these equations to be tested. Experiments in which a range of reaction mixtures has been taken to various extents of polymerization have shown that the equations are valid up to a reasonable extent of conversion. The “true” value of the transfer constant in the bromotrichloromethane/styrene system is 65±4 and apparently independent of temperature over the range 60-80°C. The energy of activation and frequency factor of the chain transfer reaction of polystyrene radicals with bromotrichloromethane are 33±5 kJ mol^–1 and 1.5 × 10⁹ l.mol^–1 s^–1 respectively. Results obtained using a g.l.c. technique support the above findings.