Shortcut to carbon dioxide plastics holds sequestration promise


The roundabout route let researchers produce a carbon dioxide polymer that is difficult to synthesise directly © NPG

Japanese scientists have cleared a significant hurdle in using carbon dioxide as a chemical feedstock and made a polymer that contains almost a third of the gas by weight. The team discovered a way to make the reaction conditions for the addition of carbon dioxide to an olefin more favourable, which they claim could make the large-scale production of carbon dioxide-based plastics possible.

Carbon dioxide is inert, so it needs a high-energy reactant to drive reactions, limiting its use as a feedstock. Some of these processes include the industrial production of urea, salicylic acid, organic carbonates and polycarbonates. Olefins are suitable co-reagents for polymerisation with carbon dioxide because they have a high potential energy owing to their carbon–carbon double bonds. But the problem is that the reaction needs so much energy to kick-start it that it typically leads to the olefins linking with up other olefins, rather than carbon dioxide.

Now, Kyoko Nozaki and her team from the University of Tokyo, Japan, have come up with a way to surmount the thermodynamic and kinetic barriers of copolymerising carbon dioxide with an olefin. The team stumbled on a solution to this problem while investigating whether it was possible to polymerise the lactone intermediate formed by the condensation of carbon dioxide and 1,3-butadiene, instead of copolymerising carbon dioxide and butadiene directly. To their surprise, they discovered that samples of the lactone intermediate underwent free radical polymerisation on its own over the course of several weeks. As previous attempts to polymerise the lactone had been unsuccessful, Nozaki was keen to investigate further.

The team found that by adding a radical initiator and an additive to the lactone the mixture polymerised in a single day to produce a polymer that was 29% carbon dioxide by weight. The new polymer also takes a lot less energy to produce as the polymerisation reaction is exothermic at -26.0kcal/mol, compared with direct addition of carbon dioxide to butadiene, which is endothermic and requires 23.9kcal/mol to go to completion.

‘This represents a clever method to circumvent the thermodynamically unfavourable direct copolymerisation of unsaturated hydrocarbons with carbon dioxide,’ says Donald Darensbourg, whose group studies carbon dioxide–epoxide copolymerisation to polycarbonates at Texas A&M University, US. ‘Developing synthetic methods to prepare new polymeric materials from carbon dioxide, in this instance a poly(ester), is important and of much current interest. Although the synthesis of the lactone monomer has previously been reported, this study is the first to discover the conditions for copolymerising butadiene and lactones.’

Nozaki’s team successfully applied their method to other reactions, including a one-pot carbon dioxide–butadiene copolymerisation and a one-pot carbon dioxide, butadiene and another 1,3-diene synthesis.  ‘The technology has the potential to finally reduce carbon dioxide emission, albeit only slightly, if it finds a market,’ says Nozaki. However, she adds that process improvements are needed.

Related Content

Green packaging blues

9 May 2014 Premium contentFeature

news image

Plastic packaging is ubiquitous, but uses precious resources and goes straight to waste. Bea Perks takes a look

The future of PVC production?

16 July 2012 Business

news image

Commercial interest in a semi-continuous approach seems to be on the rise

Most Read

Isotope effect produces new type of chemical bond

22 October 2014 Research

news image

Evidence emerges for vibrational bond first proposed 30 years ago

DNA 'barcodes' used to track food

30 October 2014 Research

news image

Milk has been successfully tracked as it is turned into cheese and yogurt in an advance that could fight food fraud

Most Commented

Square planar iron complex breaks inorganic dogma

31 October 2014 Research

news image

Unusual spin state could open the door to new and exciting chemistry

Indian U-turn on diabetes drug ban

16 August 2013 News and Analysis

news image

Suspension of cheap and popular medicine reversed but will now come with new safety warnings