DELAWARE: Eng University of Delaware with Argonne National Laboratory has been developed a chemical process which turns Styrofoam into a high-value conducting polymer PEDOT: PSS. Researchers show how good plastic waste can be functionally integrated electronic devices such as silicon-based hybrid solar cells and organic electrochemical transistors.
The research group of the corresponding author Laure Kayser, assistant professor in the Department of Materials Science and Engineering in the College of Engineering UD with a joint appointment in the Department of Chemistry and Biochemistry in the College of Arts and Sciences, regularly works with PEDOT: PSS, a polymer with electronic and ionic conductivity, and wanted to find a way to synthesize this material from plastic waste.
After a meeting with Argonne chemist David Kaphan at an event hosted by the UD research office, a team of UD and Argonne researchers began evaluating the hypothesis that PEDOT:PSS could be produced by sulfonating polystyrene, a synthetic plastic found in many types of containers and packaging. ingredient.
Sulfonation is a common chemical reaction in which a hydrogen atom is replaced by a sulfonic acid; This process is used to make various products such as dyes, drugs and ion exchange resins. The reaction may be “hard” (with higher conversion efficiency but requiring caustic reagents) or “soft” (less efficient method but using lighter materials).
In this paper, the researchers wanted to find something in the middle: “A reagent that is efficient enough to get a really high degree of functionalization but that does not mess up the polymer chain,” Kayser explained.
The researchers first turned to the method described in a previous study for the sulfonation of small molecules, which showed promising results in terms of efficiency and yield, using 1,3-Imidazolium chloride disulfonic acid ((Dsim)Cl). But adding functional groups to polymers is more challenging than for small molecules, the researchers explained, because not only are unwanted byproducts more difficult to separate, small mistakes in the polymer chain can change their overall properties.
To overcome this challenge, researchers began months of trial and error to find the optimal conditions that minimize side reactions, said Kelsey Koutsoukos, a doctoral candidate in materials science and second author of this paper.
“We screened various organic solvents, different molar ratios of sulfonating agents, and evaluated different temperatures and times to see the best conditions to achieve a high level of sulfonation,” he said.
The researchers were able to find reaction conditions that resulted in high polymer sulfonation, minimal defects and high efficiency, all while using a mild sulfonating agent. And since the researchers were able to use polystyrene, specifically Styrofoam waste, as a starting material, the method also represents an efficient way to convert plastic waste into PEDOT:PSS.
Once the researchers had PEDOT:PSS in hand, they were able to compare how their waste-derived polymers performed compared to commercially available PEDOT:PSS.
“In this paper, we look at two devices – an organic electronic transistor and a solar cell,” said Chun-Yuan Lo, a doctoral candidate in chemistry and first author of the paper. “The performance of the two types of conductive polymers is comparable, and it shows that our method is an environmentally friendly approach to turn polystyrene waste into a valuable electronic material.”
Special analyzes performed at UD include X-ray photoelectron spectroscopy (XPS) at the surface analysis facility, film thickness analysis at the UD Nanofabrication Facility, and solar cell evaluation at the Energy Conversion Institute. Argonne’s advanced spectroscopic equipment, such as carbon NMR, is used for detailed polymer characterization. Additional support was provided by materials science and engineering professor Robert Opila for solar cell analysis and by the David C. Martin, Karl W. and Renate Boer Chair Professor of Materials Science and Engineering, for electronic device performance analysis.
One unexpected discovery related to chemistry, the researchers added, is the ability to use stoichiometric ratios in reactions.
“Normally, for the sulfonation of polystyrene, you have to use an excess of very harsh reagents. Here, being able to use a stoichiometric ratio means that we can minimize the amount of waste produced,” Koutsoukos said.
This finding is one that Kayser’s group will investigate further as a way to “tune” the degree of sulfonation. So far, they have found that by changing the ratio of the starting materials, they can change the degree of sulfonation in the polymer. Along with studying how this level of sulfonation affects the electrical properties of PEDOT:PSS, the team wants to see how this fine-tuning ability can be used for other applications, such as fuel cells or water filtration devices, where the level of sulfonation is high. greatly affect the properties of the material.
“For the electronic device community, the key is that you can make electronic materials from waste, and they perform as well as you would buy commercially,” Kayser said. “For more traditional polymer scientists, the fact that you can control the degree of sulfonation efficiently and precisely will be of interest to many different communities and applications.”
Researchers also see great potential for how this research can contribute to active global sustainability efforts by providing new ways to convert waste products into value-added materials.
“Many scientists and researchers are working hard on upcycling and recycling efforts, either chemically or mechanically, and our study provides another example of how to overcome this challenge,” said Lo.
The research group of the corresponding author Laure Kayser, assistant professor in the Department of Materials Science and Engineering in the College of Engineering UD with a joint appointment in the Department of Chemistry and Biochemistry in the College of Arts and Sciences, regularly works with PEDOT: PSS, a polymer with electronic and ionic conductivity, and wanted to find a way to synthesize this material from plastic waste.
After a meeting with Argonne chemist David Kaphan at an event hosted by the UD research office, a team of UD and Argonne researchers began evaluating the hypothesis that PEDOT:PSS could be produced by sulfonating polystyrene, a synthetic plastic found in many types of containers and packaging. ingredient.
Sulfonation is a common chemical reaction in which a hydrogen atom is replaced by a sulfonic acid; This process is used to make various products such as dyes, drugs and ion exchange resins. The reaction may be “hard” (with higher conversion efficiency but requiring caustic reagents) or “soft” (less efficient method but using lighter materials).
In this paper, the researchers wanted to find something in the middle: “A reagent that is efficient enough to get a really high degree of functionalization but that does not mess up the polymer chain,” Kayser explained.
The researchers first turned to the method described in a previous study for the sulfonation of small molecules, which showed promising results in terms of efficiency and yield, using 1,3-Imidazolium chloride disulfonic acid ((Dsim)Cl). But adding functional groups to polymers is more challenging than for small molecules, the researchers explained, because not only are unwanted byproducts more difficult to separate, small mistakes in the polymer chain can change their overall properties.
To overcome this challenge, researchers began months of trial and error to find the optimal conditions that minimize side reactions, said Kelsey Koutsoukos, a doctoral candidate in materials science and second author of this paper.
“We screened various organic solvents, different molar ratios of sulfonating agents, and evaluated different temperatures and times to see the best conditions to achieve a high level of sulfonation,” he said.
The researchers were able to find reaction conditions that resulted in high polymer sulfonation, minimal defects and high efficiency, all while using a mild sulfonating agent. And since the researchers were able to use polystyrene, specifically Styrofoam waste, as a starting material, the method also represents an efficient way to convert plastic waste into PEDOT:PSS.
Once the researchers had PEDOT:PSS in hand, they were able to compare how their waste-derived polymers performed compared to commercially available PEDOT:PSS.
“In this paper, we look at two devices – an organic electronic transistor and a solar cell,” said Chun-Yuan Lo, a doctoral candidate in chemistry and first author of the paper. “The performance of the two types of conductive polymers is comparable, and it shows that our method is an environmentally friendly approach to turn polystyrene waste into a valuable electronic material.”
Special analyzes performed at UD include X-ray photoelectron spectroscopy (XPS) at the surface analysis facility, film thickness analysis at the UD Nanofabrication Facility, and solar cell evaluation at the Energy Conversion Institute. Argonne’s advanced spectroscopic equipment, such as carbon NMR, is used for detailed polymer characterization. Additional support was provided by materials science and engineering professor Robert Opila for solar cell analysis and by the David C. Martin, Karl W. and Renate Boer Chair Professor of Materials Science and Engineering, for electronic device performance analysis.
One unexpected discovery related to chemistry, the researchers added, is the ability to use stoichiometric ratios in reactions.
“Normally, for the sulfonation of polystyrene, you have to use an excess of very harsh reagents. Here, being able to use a stoichiometric ratio means that we can minimize the amount of waste produced,” Koutsoukos said.
This finding is one that Kayser’s group will investigate further as a way to “tune” the degree of sulfonation. So far, they have found that by changing the ratio of the starting materials, they can change the degree of sulfonation in the polymer. Along with studying how this level of sulfonation affects the electrical properties of PEDOT:PSS, the team wants to see how this fine-tuning ability can be used for other applications, such as fuel cells or water filtration devices, where the level of sulfonation is high. greatly affect the properties of the material.
“For the electronic device community, the key is that you can make electronic materials from waste, and they perform as well as you would buy commercially,” Kayser said. “For more traditional polymer scientists, the fact that you can control the degree of sulfonation efficiently and precisely will be of interest to many different communities and applications.”
Researchers also see great potential for how this research can contribute to active global sustainability efforts by providing new ways to convert waste products into value-added materials.
“Many scientists and researchers are working hard on upcycling and recycling efforts, either chemically or mechanically, and our study provides another example of how to overcome this challenge,” said Lo.
