Argonne Research targets e-waste with biodegradable polymers

From your car’s navigation screen to the screen you’re reading this on, luminescent polymers—a class of flexible materials containing light-emitting molecules—are used in a variety of today’s electronics. Luminescent polymers stand out for their light-emitting ability, together with their extraordinary flexibility and extensibility, showing great potential in various application fields.

However, once these electronic devices reach their end use, they are discarded, piled up in landfills or buried underground. Recycling this e-waste is complex, requiring expensive and energy-inefficient processes. Although there is an economic incentive to recycle key semiconductor materials—in this case, luminescent polymers—there has been no method to achieve this because of the challenge of designing these materials at the molecular level.

“We were able to make this material biodegradable and recyclable without sacrificing functionality.” — Jie Xu, Argonne scientist who led the project

Overcoming this challenge was the motivation for the newest issue of Nature Sustainability, led by researchers at the US Department of Energy’s (DOE) Argonne National Laboratory, along with collaborators at the University of Chicago, Purdue University and Yale University. The team developed a strategy to design luminescent polymers with high light-emitting efficiency from scratch that are biodegradable and recyclable. They do this by incorporating a chemical called tert-butyl ester into the luminescent polymers, which can break down when exposed to heat or mild acid.

In short, this chemical enables material recycling while maintaining high light emission functions.

The team then used a device to test the material’s external quantum efficiency, an indicator of light source performance. It scored an impressive 15.1% in electroluminescence, a tenfold increase over existing degradable luminescent polymers.

At the end of life, this new polymer can be degraded either under mildly acidic conditions (near stomach acid pH) or relatively low heat treatment (> 410 F). The resulting materials can be isolated and turned into new materials for future applications.

“We were able to make this material biodegradable and recyclable without sacrificing functionality,” said project leader Jie Xu, a scientist at the Center for Nanoscale Materials, a DOE Office of Science user facility at Argonne. “This work serves as an important benchmark in addressing the urgent need for sustainability in the design of future electronics.”

The team aims to make future electronics more sustainable (easier to degrade or recycle) and not just design for actual function. They also want to expand the usability of these products in other areas.

“The design is still compatible with the processability, and in the end, you have to use this in real applications,” said Yuepeng Zhang, a materials scientist at Argonne and co-author of the paper. The researchers predict that this new polymer could be applied to existing technologies, such as displays and medical imaging, and enable new applications.

The next steps for scaling the technology include moving it from the lab to electronics such as cell phones and computer screens with continuous testing.

The team noted that this is only a first step in the process, but with e-waste, every step counts. Xu hopes more attention will be paid to designing electronics with recyclability in mind, especially since this depolymerization proof of concept was so successful.

“This is a $46 billion a year industry and it’s only growing,” Xu said. “By 2032 the industry is estimated to grow to $260 billion. With this method, we can eliminate this type of e-waste that would otherwise end up in landfills.”

Other Argonne authors include Wei Liu, Aikaterini Vriza, Hyocheol Jung, Shiyu Hu, Benjamin T. Diroll, Richard D. Schaller, and Henry Chan. Other authors include Yukun Wu and Sihong Wang (Argonne, Purdue University), Cheng Zhang, Glingna Wang (University of Chicago), Du Chen, Peijun Guo (Yale University), and Jianguo Mei (Purdue University).

Funding was provided by a Directed Research and Development award from Argonne Laboratory, the National Science Foundation and the US Air Force Office of Scientific Research.

About the Argonne Center for Nanoscale Materials