Plastic oranges

A Cornell University research group has discovered how to make a new type of plastic by using a catalyst to combine limonene oxide and CO2.

Geoffrey Coates, a Cornell professor of chemistry and chemical biology, and his graduate students Chris Byrne and Scott Allen have discovered a way to make polymers using limonene oxide and carbon dioxide, with the help of a catalyst developed in the researchers’ laboratory.

Limonene is a carbon-based compound produced in more than 300 plant species. In oranges it makes up about 95 percent of the oil in the peel.

In industry, Coates explains, the orange peel oil is extracted for various uses, such as giving household cleaners their citrus scent. The oil can be oxidised to create limonene oxide.

By using their catalyst to combine limonene oxide and CO2, the Coates group produced a novel polymer, called polylimonene carbonate, that has many of the characteristics of polystyrene.

“The polymer is a repeating unit, much like a strand of paper dolls. But instead of repeating dolls, the components alternate between limonene oxide and CO2 — in the polymer,” says Coates. Neither limonene oxide nor CO2 form polymers on their own, but when put together, a promising product is created.

The Coates research team is particularly interested in using CO2 as an alternative building block for polymers. Instead of being pumped into the atmosphere as a waste product, CO2 could be isolated for use in producing plastics, such as the team’s polylimonene carbonate.

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