Careful "Sulfonation" Turns Waste Polystyrene, Styrofoam Into a Valuable Electronics Resource

Researchers from the University of Delaware and Argonne National Laboratory have developed a way to convert polystyrene, a common hard-to-recycle waste plastic, into functional electronic devices — making what was once a trash into a treasure.

"In this paper, we looked at two devices — an organic electronic transistor and a solar cell," explains Chun-Yuan Lo, a chemistry doctoral candidate first author on the team's paper. "The performance of both types of conductive polymers was comparable, and shows that our method is a very eco-friendly approach for converting polystyrene waste into high-value electronic materials."

DuPont's Styrofoam and generic polystyrene are extruded and expanded plastic foams, respectively, commonly used as insulation and protective padding — and usually thrown away, which given its entirely non-biodegradable state is suboptimal. Instead of disposing of the waste, the team's approach turns it into something valuable: poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), a conductive polymer used in a range of electronic endeavors.

Through months of trial and error, the researchers were able to develop a method for sulfonation — required to process polystyrene into PEDOT:PSS — which uses a minimum of harsh chemical reagents, reducing the usual waste. Tuning the sulfonation process also allows for controlling the final material, with future research to investigate using the approach for raw materials to be used in fuel cells, water filters, and other fields.

"For the electronic devices community, the key takeaway is that you can make electronic materials from trash, and they perform just as well as what you would purchase commercially," corresponding author Laure Kayser concludes. "For the more traditional polymer scientists, the fact that you can very efficiently and precisely control the degree of sulfonation is going to be of interest to a lot of different communities and applications."

"Many scientists and researchers are working hard on upcycling and recycling efforts, either by chemical or mechanical means," Lo adds, "and our study provides another example of how we can address this challenge."

The team's work has been published under open-access terms in the journal JACS Au.