Opening a molecular ring offers a new route to sustainable polymers

The urgent need to reduce dependency on petroleum-based materials is motivating researchers to explore more sustainable chemical options. A team at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have produced polyglycolides, a form of polyester, from the small cyclic glycolide molecule which can be extracted from plants. They report their findings in the Journal of the American Chemical Society.

Glycolide has a ring of carbon and oxygen atoms that must be broken open to create molecules that can repeatedly combine into a polymer chain. This has previously been difficult, due to the low solubility of the polymers in the solvents needed to accommodate the reaction.

To overcome this challenge, the KAUST team used fluorinated alcohol solvents. The synthesis reaction occurs quickly at room temperature, while the product can be readily recycled by a simple chemical procedure at the relatively low temperature of 200 °C.

This is also the first glycolide-linking process that achieves what polymer chemists call a ‘living/controlled’ reaction, meaning that the end of the growing polymer chain has the reactivity needed to allow the chain-building process to continue. The researchers say that other chemical blocks could in future be incorporated into the chain, greatly increasing the range of potential products.

“Many researchers believed this process could not be possible in the type of solvents we used,” says polymer chemist, Nikos Hadjichristidis, who led the research. “Our work shows it could become part of a circular carbon economy.”

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