Metalloporphyrin catalyzed self-switchable terpolymerization of propene oxide, phthalic anhydride and lactide for one-pot prepare block copolyesters

Abstract

The copolymerization of polylactic acid with other monomers or polymers can enhance its performance and expand its range of applications. In this work, a range of metalloporphyrin catalysts featuring diverse substituents and metal coordination centers were synthesized and employed in conjunction with co-catalyst bis(triphenylphosphoranylidene) ammonium chloride (PPNCl) for the terpolymerization of phthalic anhydride (PA), propylene oxide (PO), and lactide (LA) ester without the use of initiators. The catalytic activity of the porphyrin ligand is significantly influenced by its substituents and different metal centers. Under optimal conditions, catalyst TOMePP-CoCl exhibits the most outstanding reactivity among all catalysts. In particular, this terpolymerization is a one-pot self-switching polymerization catalyzed by the metalloporphyrin/PPNCl system. PA selectively undergoes ring-opening copolymerization with PO first, while LA remains inert until PA totally consumed. Through continuous feeding experiments, a multiblock copolymer with fine structure controllability was successfully synthesized, which has been verified by DOSY NMR analysis.