UV used to make recyclable, sustainable polymers

Scientists have used ultraviolet (UV) light to successfully synthesise more sustainable and recyclable polymer materials. Led by green chemistry experts at Flinders University, and published in the Journal of the American Chemical Society, the development is a major step in making polymers high in sulfur content for more sustainable plastic alternatives using waste materials.

Over the past decade, the Flinders University team has shown these highly flexible sulfur-rich polymers can be used in a wide range of high-value applications — from lithium–sulfur battery cathode components and heavy metal land and water remediation as well as optics for infrared imaging and even novel antimicrobial agents. This latest research promises to make them even more adaptable and affordable.

“We show these remarkable new polymers can be produced in more sustainable ways, and also recycled using low-cost accessible energy sources including UV light and LED, as well as using other methods,” said lead author and Australian Research Council Discovery Early Career Research Award fellow Dr Thomas Nicholls, from the College of Science and Engineering at Flinders University.

In the latest study, an interdisciplinary team from Flinders University, the University of Tasmania and Deakin University was able to produce sulfur-rich polymers by simply shining UV light on the monomer building blocks to connect them together.

The newly developed method also used pulsed LED (energy-efficient light emitting diode) to reshape the polymer monomer to increase its green credentials.

“While the UV light breaks sulfur–sulfur bonds to begin with, we used short bursts of LED irradiation to overcome degradation in polymerisation,” Nicholls said. “This technique allowed the synthesis of high molecular weight polymers which allowed them to be used in several applications such as recyclable adhesives, new photoresists for lithography, and anti-corrosion coatings.”

The research project team used UV light, or heating above 150°C, to recycle the polymers — making it possible for the monomer building blocks to be polymerised again and reused.

Co-author Dr Jasmine Pople said the team’s latest discovery enables the synthesis of high molecular weight sulfur polymers by simply switching on and off a light.

“This approach encompasses mild, safe and sustainable conditions, providing ready access to sulfur polymers,” Pople said.

Flinders University author Dr Harshal Patel said the application of flashing light at a steady 60 beats per minute was “an exciting project, exploring yet more applications for chemical recyclability of these polymers, as well as the mechanistic analysis”.

Image caption: Dr Harshal Patel, Dr Jasmine Pople and Dr Thomas Nicholls. Image: Supplied.