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.

Automated summary

The development of chemically recyclable polymers with closed-loop life cycles is considered the most attractive strategy for creating a circular plastic economy. In this study, enantiopure O-heterocyclic lactones with pendent phenyl substituent were successfully prepared and used as raw materials to synthesize poly(ether-ester)s with controlled molecular weights, narrow dispersities, and well-defined terminal groups. The monomer stereoconfiguration significantly affects the polymerization kinetics, thermodynamics, and thermal/mechanical properties of the resulting polyesters. Both resultant polymers demonstrated closed-loop recyclability, and depolymerization back to pristine monomers was easily achieved using stannous octoate as the catalyst in solution.