A rare example of closed-loop chemical recycling

28 January 2021 | Muriel Cozier

‘I honestly think this is one of the most important things to ever come out of my lab.’

A team of researchers from the US’ Princeton University Department of Chemistry have discovered a molecule which they say could one day make closed-loop recycling a reality.

Publishing the findings in Nature Chemistry, the research team says that the molecule, which is a form of polybutadiene, and is known as oligocyclobutane, connects in an unusual way as a repeating sequence of squares. This formation allows the polymerisation the process, under certain conditions, to be reversed, effectively taking the polymer back to its monomer state. The researchers describe the process as being ‘zipped up’ to create the polymer and ‘unzipped’ to depolymerise the material.

Led by Paul Chirik, the Edwards S. Stanford Professor of Chemistry, the team explores sustainable chemistry by investigating the use of iron to build new molecules. In this particular research, the team says that iron ‘persuades’ the monomer to click together to make the polymer chain of squares. The polymer is ‘unzipped’ by exposing it to a vacuum in the presence of an iron catalyst. This, say the researchers is ‘a rare example of closed-loop chemical recycling.’

Professor Chirik said ‘You can make really tough materials out of this monomer. What people tend to assume is that when you have a chemically recyclable polymer, it has to be somehow inherently weak or not durable. We’ve made something that’s really, really tough but also chemically recyclable. We can get pure monomer back out of it, and that surprised me.’

Professor Chirik added ‘I honestly think this is one of the most important things to ever come out of my lab.’

DOI: 10.1038/s41557-020-00614-w

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