A thermally robust β-diketiminate zinc initiator for high-temperature bulk polymerization of β-butyrolactone toward high-molecular-weight poly(3-hydroxybutyrate).

β-Diketiminate (BDI)-supported zinc complexes are among the most efficient initiators for the ring-opening polymerization (ROP) of β-butyrolactone (BBL), but their application in high-temperature bulk polymerization is limited by initiator deactivation. To improve thermal robustness, a new BDI-supported zinc initiator incorporating a 2,6-bis(diphenylmethyl)-4-methylphenyl substituent was designed, synthesized, and structurally characterized. Compared with a conventional BDI-supported zinc initiator, the new complex exhibits superior performance in the bulk polymerization of BBL at elevated temperatures, affording colorless poly(3-hydroxybutyrate) (PHB) with number-average molecular weights up to 187 000 g mol-1 under solvent-free conditions. The enhanced polymerization performance is attributed to improved thermal robustness arising from the suppression of initiator deactivation during high-temperature polymerization.