On the mechanism of the radical polymerization of vinyl chloride

The mechanism of precipitation polymerization of vinyl chloride was studied by gradual transition from homogeneous to heterogeneous polymerization. Diethyl oxalate and 2,4‐dichloropentane were used as solvents. In diethyl oxalate the initial course of polymerization is homogeneous up to 7.5 moles/l. The order with respect to monomer is 1.2. At higher concentration of monomers, the order decreases due to aggregation. From about 10 moles/l, the polymerization is heterogeneous. A break is observed in the kinetic curves with a distinct acceleration accompanied by a decrease of the order with respect to monomer and of the degree of polymerization. In the presence of CBr4 the polymerization is heterogeneous in the whole range of monomer concentration studied. In 2,4‐dichloropentane the initial rate is lower than in diethyl oxalate and the order with respect to monomer is 1.6. It was shown that in the initial course of precipitation polymerization the propagation rate decreases to such an extent that a termination reaction besides the transfer to monomer bimolecular termination must be taken into consideration.