Overview and assessment of recent research on the structural defects in poly(vinyl chloride)

New mechanistic studies of structural defect formation in ordinary poly(vinyl chloride) (PVC) are summarized and critiqued. Evidence relating to the creation of some of the internal double bonds is tentatively suggested to imply the occurrence of hydrogen transfer via one or more cyclic transition states having ≥9 ring atoms. The absence of free chlorine atoms from polymerizations of vinyl chloride (VC) is reaffirmed, and a new mechanism, not yet verified, is identified as a possible explanation for a reported enhancement of the chloromethyl branch concentration at high conversions of monomer. This mechanism involves an intramolecular 1,5 hydrogen shift in a 1,3,5,6-tetrachlorohexyl radical. Copolymerization of VC with the chloroallylic chain ends of PVC is argued to be insignificant, and the new information in the literature is shown not to invalidate the currently accepted chemistry for the polymerization of vinyl chloride by standard free-radical methods.