Synthesis and Ring-opening Polymerization of Benzoxy Substituted Oxa-lactones

This study described the efficient synthesis of two oxolactone monomers ((3R, 7R) -M1 and (3S, 7R)-M2). The monomers were synthesized using (R)-methyl-3-hydroxybutyrate, which is an alcoholysis product of poly(3-hydroxybutyrate) (P3HB). The introduction of phenoxymethyl resulted in diastereoisomers with different polarity that could be separated by column chromatography. The monomers were polymerized via ring-opening polymerization using MeAl[salen] as the catalyst, and the polymerization behaviour was investigated. P((3R,7R)-M1) and P((3S, 7R)-M2) with controlled molecular weights and chain- end groups were prepared. The linear structure of the polymers was further confirmed using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) and H-1 nuclear magnetic resonance (1H-NMR). P((3S, 7R)-M2) is a semi-crystalline polyester. Additionally, stannous octanoate (Sn(Oct)(2) was used as a catalyst to achieve the depolymerization and recovery of the P((3R, 7R)-M1) in a dilute solution of 1,3,5-mono-trimethylbenzene. This strategy enables P3HB upcycling, extending the material's life cycle and expanding the range of high-value closed-loop recyclable polyether esters.

Automated summary

This study described an efficient synthesis of two oxolactone monomers using an alcoholysis product of poly(3-hydroxybutyrate) (P3HB). The monomers were polymerized and the behavior of polymerization was investigated. The resulting polymers had controlled molecular weights and end groups. Additionally, the study achieved the depolymerization and recovery of the polymer using a catalyst, extending the material's life cycle.