The thermal depolymerization of polystyrene. VI. Investigation of „weak links” by ozonization

The initial decrease in the molecular weight of polystyrene on ozonization is, within experimental error, the same as that which occurs during thermal weak link scission. In addition, the molecular weight of polystyrene in which weak links have been destroyed thermally does not further decrease on ozonization. Thus it is deduced that the weak links in polystyrene are associated with unsaturation in the main polymer chains. Taken in conjunction with previous work this evidence has led to the proposition that weak links are associated with quinonoid type structures formed during polymerization by reaction of polystyryl radicals in one of the resonance forms in which the radical centre exists in the benzene ring. A non‐radical mechanism for thermal weak link scission is proposed which satisfies all the experimental findings.