New Polymer Research Offers Route to Tough Sustainable Materials

Oxford researchers, including Trinity DPhil student Kam Poon, have developed a versatile and simple strategy to enhance and alter the properties of sustainable polymers. 

Thermoplastic elastomers (TPEs) are attractive alternative materials to vulcanized rubber as they exploit physical crosslinking opposed to chemical crosslinking which allows for mechanical recycling. TPEs are currently used in a wide range of sectors, from the automotive industry to healthcare and have an annual global production approaching 5.55 megatons, with a market value of nearly $34 billion. However, they are largely derived from petroleum and have limited abilities to degrade at their end-of-life. 

A team in the Department of Chemistry at the University of Oxford have been developing new, oxygenated, sustainable TPEs which are made from bio-derived sources and/or carbon dioxide (CO₂). In order to make these exciting and novel materials more industrially attractive, the thermomechanical properties must be improved to rival and outperform the petroleum derived market leaders.  

Kam and co-workers have developed a generally applicable method to augment thermomechanical properties without the need for complete material re-design. By selectively functionalising TPEs with reversible metal-carboxylate crosslinks, the elastomers can exhibit an over 50-fold increase in stiffness and 21-fold increase in strength without compromising elastic recovery. By employing small quantities of different Earth abundant metals (sodium, magnesium, calcium, zinc and aluminium) these ionomeric materials have wide operating temperatures, high creep-resistance and remain recyclable and degradable. 

It is hoped that in future, these materials could substitute high-volume petrochemical elastomers and be used in rapidly developing fields like medicine, electronics and robotics. 

Led by Trinity Professorial Fellow Charlotte Williams OBE FRS, the work has been published in the journal Advanced Materials. 

Kam Poon is a DPhil student from Oxford’s Department of Chemistry and is funded by the Oxford Inorganic Chemistry for Future Manufacturing Centre of Doctoral Training. Kam, first author on the work, said: ‘It is critical we can easily and efficiently improve the properties of sustainable polymer materials to encourage industry to switch from petroleum feedstocks to sustainable alternatives.’ 

‘The beauty of this functionalization strategy is how easy it is to tune material properties. By carefully selecting the metal used and the quantity employed we can manipulate the strength, stiffness, toughness and maximum strain the material can exhibit with the resulting materials remaining colourless and reprocessable. We hope this study is just the start, this approach can easily be expanded to many other classes of polymer materials and used to create an exciting new generation of future materials. I am so grateful for the amazing team I get to work in every day. Without their support and mentorship this work wouldn’t have been possible.’ 

Kam is continuing to synthesis and develop new CO₂- and bio-derived materials as well as new approaches to fabricate them in his DPhil work. The team hope these new materials will help push us towards a greener polymer future.