Binaphthalene-Modified C-Scorpionate Zinc Catalysts for Ring-Opening Polymerization of Bio-Based γ-Ketolactones to...

The metal-catalyzed ring-opening polymerization (ROP) of cyclic (di)esters is a key strategy for producing sustainable polyesters, yet the development of robust, efficient, and tunable catalysts remains a major challenge. Herein, we reported a series of zinc catalysts supported by poly(1H-pyrazol-1-yl)methane (C-scorpionate) ligands for the controlled ROP of 4,4,6,7-tetramethyloxepane-2,5-dione (MeOPD), a bio-derived γ-ketolactone obtained from ketoisophorone. Ligand framework optimization afforded a highly active and stable binaphthalene-containing zinc complex, enabling the synthesis of degradable polyesters with absolute M_w > 900 kDa and M_n > 800 kDa. Mechanistic studies revealed that steric and electronic features of the ligand suppress catalyst aggregation and stabilize the Zn─OR species. Furthermore, the catalyst exhibited remarkable tolerance to excess alcohols, allowing for precise molar mass control even at low catalyst loadings while maintaining polymerization efficiency. Tensile testing confirmed improved mechanical properties of the resulting polyesters with increasing molar mass, while photodegradation studies demonstrated efficient UV-triggered degradation enabled by backbone ketone functionalities. These findings offer important insights into catalyst design for next-generation sustainable polymers.