Pyrolysis of α‐ and β‐deuterostyrene polymers

Recently the depolymerization of addition polymers has been treated in terms of four elementary reactions: initiation, propagation, transfer, and termination; analogous to those reactions which operate in the polymerization process. It is the transfer process which, according to its relative importance, gives rise to differences in polymers in the monomer yield, in the rate vs. conversion behavior, and in the molecular weight vs. conversion behavior. The transfer process is assumed to operate through the abstraction of a hydrogen from the polymer chain by a radical. By substituting a deuterium for the hydrogen at selected points in the polymer chain, the amount of the transfer process should be decreased due to an isotope effect. Two deuterated polymers were made from α‐ and β‐deuterated styrenes and their depolymerization behavior studied. In the case of the α‐deuterostyrene polymer the results are compatible with a ½ decrease in the rate of the transfer process and also an increase in the rate of the propagation. The results with the β‐polymer imply an increase in both the transfer and propagation rates. The data obtained indicate that in polystyrene the intermolecular transfer process is mainly responsible for the fall in molecular weight of the polymer residue during depolymerization.