Depolymerization of Polyolefins by Ethenolysis Reaction: a Feasibility Study Using a Model Polyoctenamer

The possibility of depolymerizing dehydrogenated polyolefins containing double bonds in the chain using the ethenolysis reaction on Grubbs catalysts was studied. Commercial polyoctenamer was used as a model of the dehydrogenated polymer. It was shown that the first generation Grubbs catalyst and the Grubbs–Hoveyda catalyst effectively reduce the molecular weight of the polyoctenamer even at room temperature. An increase in temperature promotes both an increase in the ethenolysis rate and a decrease in the polymer molecular weight. In the presence of the Grubbs–Hoveyda catalyst at 45°C, it was possible to reduce the molecular weight of the polyoctenamer from 120 000 to 480 Da. It was established that the ethenolysis of specially prepared dehydrogenated polyethylene is primarily lead to the isomerization of terminal double bonds with their migration into the chain; effective depolymerization is hindered by the poor solubility of the polymer in the reaction medium.