3-methylphenol alkoxy aluminum complexes for ring-opening polymerization of ε-caprolactone under mild conditions

A novel class of 3-methylphenol alkoxy aluminum complexes was developed for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) under mild conditions (60 °C, 30 min). Through systematic optimization of Al/CL molar ratios (5:1000 ~ 4:1000), monomer concentrations (1 mol/L), and reaction parameters, high polymer yield (99.9% ± 0.1%) was achieved, yielding polycaprolactone (PCL) with tunable molecular weights (M n up to 34 kg/mol) and narrow dispersity (PDI = 1.38). Structural characterization via 1 H NMR and FTIR confirmed successful PCL formation. GPC analysis validated controlled chain growth and uniformity (PDI < 1.5), while thermal properties were assessed via DSC and TGA, showing semicrystalline behavior and high thermal stability. Kinetic studies showed linear molecular weight progression with polymer yield, while sequential monomer feeding experiments confirmed living polymerization characteristics, with M n increasing proportionally and maintaining low PDI. Compared to conventional metal-based systems, this catalytic platform operates at lower temperatures with reduced toxicity risks, enabling energy-efficient synthesis of biodegradable polyester for biomedical and packaging applications.