Bis-ligated zinc complexes supported by tridentate ketoiminate ligands with electron-donating and varying steric properties were synthesized and investigated as ring-opening polymerization (ROP) initiators. The complexes were characterized with NMR and absorbance spectroscopy and were activated for ROP by a co-catalyst, 4-fluorophenol (4FP). The complexes were fast and effective for L-lactide (LA) ROP with 99 % conversion to poly-lactic acid (PLA) in 2 h at 100 °C. ε-Caprolactone (CL) polymerization to poly-caprolactone (PCL) was slower at 100 °C only achieving 16 % conversion in 24 h which increased to 96 % conversion in 24 h at 135 °C. Copolymerization of LA and CL was investigated, and PCL-b-PLA block copolymer was prepared through the sequential addition of CL (90% conversion in 24 h) followed by LA (99% conversion in 2 h). The polymer (PLA and PCL) and copolymer (PCL-b-PLA) materials were isolated and characterized with gel permeation chromatography, nuclear magnetic resonance, and differential scanning calorimetry.

Synthesis of bis-ligated zinc complexes and their use in ring opening (co-)polymerization of L-lactide and ε-caprolactone

2019 Spring National Meeting

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