AbstractVinyl chloride (M) was polymerized in the presence of a low molecular weight polybutadiene (S) at 60°C in the presence of x,x′‐azobisdiisobutyronitrile as initiator, which does not affect the transfer reaction.The raw material was fractionated for the purpose of separating the pure PVC homopolymer.The number‐average molecular weight of PVC homopolymer, determined by size exclusion chromatography (SEC), was used in Mayo's equation to obtain the value of the transfer constantCs, which was found to be 11. A simplified reaction scheme is given according to which it is possible to explain why the reaction yield decreases and the crosslinking density increases by increasing the [S]/[M