Crystalline Stereoregular Poly(ether-ester) via MeAl[Salen]-Catalyzed Well-Controlled Ring-Opening Polymerization of Enantiopure Cyclic Ether-Ester Monomer

Thedevelopment of chemically recyclable polymers with closed-looplife cycles is believed to be the most attractive strategy in creatingthe circular plastic economy. Here, we successfully prepared a pairof enantiopure O-heterocyclic lactones bearing withpendent phenyl substituent, which are named (2S,7R)-7-methyl-2-phenyl-1,4-dioxepan-5-one (SR-M1) and (2R,7R)-7-methyl-2-phenyl-1,4-dioxepan-5-one(RR-M2), respectively, by using the methanolysisproduct of poly(3-hydroxybutyrate) (P3HB) as the raw material. Thewell-controlled ring-opening polymerizations of SR-M1 and RR-M2 were achieved in the presence of MeAl[salen]as the catalyst to produce poly(ether-ester)s with controlled molecularweights, narrow dispersities, and well-defined terminal groups. Themonomer stereoconfiguration has a big impact on their polymerizationkinetics and thermodynamics as well as the thermal and mechanicalproperties of resultant polyesters. Both the resultant P(SR-M1) and P(RR-M2) exhibited closed-loop recyclability.The depolymerization of resultant polyesters back to pristine monomerscan be easily realized using stannous octoate as the catalyst in solution.