Low-energy, environmentally friendly polymer production

Chemistry researchers at Flinders University have discovered a new way to make ‘green’ polymers from low-cost building blocks with a small amount of electricity. The reaction is fast and occurs at room temperature, with no hazardous chemical initiators required — just electricity. Potential uses include gold mining and recycling e-waste. The research findings were published in the Journal of the American Chemical Society.

Co-author Dr Thomas Nicholls, an expert in using electrochemistry to make valuable molecules, said the use of electricity to produce new materials is an emerging field of research that opens many doors to new chemicals and polymers that can be produced in a more sustainable way. The process begins by adding an electron to the basic building block or monomer. After ‘electrocuting’ the monomer, it reacts with another building block in a chain reaction which leads to the formation of a polymer.

First author Jasmine Pople said the researchers’ method to electrochemically produce polymers provides new materials that are highly functional and environmentally friendly. “The use of electricity to make valuable molecules is expanding rapidly due to its versatility. Additionally, it may generate less waste than traditional chemical syntheses and it can be powered with renewable energy,” Pople said.

The key polymer made by the team has sulfur-sulfur bonds in its backbone. These sulfur groups can be used to bind precious metals such as gold. The team demonstrated that the key polymer could remove 97% of gold from solutions of relevance to mining and e-waste recycling. The sulfur-sulfur bonds can also be broken and reformed — this interesting property enabled researchers to discover conditions to convert the polymer back to its original building block, in an important advancement in recycling.

Typically, when common plastics are recycled, they are heated and reshaped into a new product. This process can cause degradation and down-cycling (conversion to a less valuable material), leading to eventual disposal in landfill. The polymers made in the latest research can be chemically converted back to their constituent building blocks in high yield — meaning that building block can be used again to make new polymers. The researchers also carried out quantum mechanical calculations to understand the details of how the reaction works.

“The polymerisation has a clever self-correcting mechanism: whenever the wrong reaction occurs, it reverses until the correct reaction proceeds, ensuring a uniform polymer,” said Dr Le Nhan Pham, Research Associate in computational and physical chemistry.

Future applications for these materials include environmental remediation, gold mining and use of the polymer as an anti-microbial agent.

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