The electronic effects on ring-opening polymerization (ROP) of ε-caprolactone (εCL) and L-lactide (LA) resulting from incorporation of trifluoromethyl groups into the five-coordinate aluminum complexes was studied with computational and experimental methods. Kinetic time courses showed a linear relationship between time and ln [monomer] for both εCL and LA. Polymerization activity increased with increasing numbers of trifluoromethyl groups (n = 0, 1, or 2) on the ketoiminate supporting ligand. These results were verified by the DFT-computed energetic parameters of the activation energies. Transition state energies decreased with increasing numbers of trifluoromethyl group for the ROP of the first and second εCL monomers into the polymer chain. The kinetic results and the transition state energies demonstrated that incorporation of the trifluoromethyl groups increased electrophilicity/Lewis acidity of the aluminum center. Preliminary data showed these trends were repeated for the kinetics and energetics of LA ROP.

Computational and experimental comparative study on the ring-opening polymerization of ε-caprolactone and L-lactide by aluminum ketoiminate complexes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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