Polymerization of ε-Caprolactone Using Bis(phenoxy)-amine Aluminum Complex: Deactivation by Lactide

Reviving biomedical polymer production

31 July 2019

Understanding a quirk in the catalytic production of medical-grade polymers could lead to better catalysts, and new ways of preparing polymers with specific properties, a team led by Vidyasirimedhi Institute of Science and Technology (VISTEC) researchers has shown.

Due to their biocompatible and biodegradable nature, polymers made from the cyclic esters caprolactone or lactide have applications ranging from dissolvable sutures to drug-delivery materials. A range of catalyst systems can convert these starting materials into polymers.

Despite their chemical similarity, caprolactone and lactide can have very different polymerization rates with aluminium-based catalysts. VISTEC researchers and their collaborators have used techniques including nuclear magnetic resonance and X-ray crystallography to probe this observation.

The team found that the lactide molecule, which is a slightly smaller cyclic ester with additional oxygen functionality compared to caprolactone, can bind to the catalyst and deactivate it. Heating the deactivated catalyst, even after several hours in the dormant state, could reactivate it to complete the reaction.

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References

1. Inorganic Chemistry 57, 10170–10179 (2018). doi: 10.1021/acs.inorgchem.8b01364