The kinetics of depolymerization of addition polymers

The kinetics of random and end-initiated depolymerization are examined taking into account distribution of molecular sizes. It is shown that for a sample undergoing random scission with complete unzipping the breadth of the distribution of molecular weights as measured by the ratio P w / P n has a marked effect on the relationships between sample weight, molecular weight, and time. Furthermore the molecular weight/conversion curves for this condition lie in the area of the graph which hitherto had been assumed to indicate end-initiated depolymerization uniquely. It is proposed that the order of the reaction with respect to weight of sample is a reliable guide to the mechanism of initiation. On the experimental side it is suggested that interpretation of thermogravimetric analysis data in depolymerization experiments must be made in light of the fact that the order of the reaction will alter once the molecular population changes due to loss of molecules, and since distribution of molecular weights has such a marked effect on randomly initiated reactions, this parameter should be measured in experimental investigations of depolymerization.