Degradation of poly(propylene carbonate) by coordination catalysts containing phenolatozinc and alcoholatozinc species

Abstract

AbstractPoly(propylene carbonate) was treated with coordination catalysts exhibiting activity in propylene oxide/carbon dioxide copolymerization and cyclization. Poly(propylene carbonate) was found to undergo degradation and depolymerization reactions which were monitored by intrinsic viscosity of the polymer and the yield of propylene carbonate. End‐groups in the degraded polymer were determined using ultraviolet spectroscopy. Catalysts containing active phenolatozinc species were shown to cleave the poly(propylene carbonate) chain introducing to it the aryloxy moiety as aryl carbonate end‐group and the zinc moiety as alcoholatozinc end‐group. On the contrary, catalysts containing active alcoholatozinc species were shown to cleave the poly(propylene carbonate) chain introducing to it the alcoholate moiety as alcoholate end‐group and the zinc moiety as alkylcarbonatozinc end‐group. Propylene carbonate formation was proposed to occur involving chain depolymerization via alcoholatozinc end‐groups. Propylene carbonate formation involving chains terminated with alkylcarbonatozinc groups was proposed to be preceded by their decarboxylation with CO2 elimination leading to alcoholatozinc end‐groups.