Mechanism of the polymerization of vinyl chloride and chloroprene in the presence of transition‐metal complexes

To clarify the polymerization mechanism of vinyl chloride (VCl) and chloroprene (CP) with titanium tetrabutoxide‐aluminum alkylchlorides some work was carried out. Carbon tetrachloride surprisingly enhanced polymerization without decreasing the molecular weight, whereas carbon tetrabromide transferred the polymer chain. The monomer reactivity ratios in the copolymerization of VCl with vinylidene chloride (VdCl), rVCl = 0.30 and rVdCl = 0.90, differed from those in free‐radical polymerizations. In the polymerization of perdeuterovinyl chloride an ethyl radical originating from AlCl(C2H5)2 was found to be incorporated into the polymer. Polymerization of chloroprene with the same catalyst in carbon tetrachloride was kinetically investigated, and a square‐root dependence of the catalyst concentration on the rate was seen. With vanadyl or cobalt acetylacetonate polymers of identical microstructure were obtained. Copolymerization with butadiene and styrene revealed the same behavior as that in free‐radical polymerization. It is suggested that in the polymerization with this catalyst an ionic or coordinated mechanism is included besides the usual radical mechanism.