Q&A: Ryan Fellow, NU student Matthew Coile discusses recyclable plastic research

Photo courtesy of Matthew Coile

Fourth-year chemical engineering Ph.D. student Matthew Coile collaborates with McCormick Prof. Linda Broadbelt to research methods to recycle typically “unrecyclable” network polymer plastics, such as polyurethanes.

Fourth-year chemical engineering Ph.D. student Matthew Coile received the Ryan Fellowship in 2019 for his work in chemical and biological engineering. 

The fellowship supports graduate students interested in applying nanotechnology to practical applications that benefit society, according to the International Institute for Nanotechnology. 

Coile works with McCormick Prof. Linda Broadbelt to design highly recyclable plastics. An October report by Greenpeace found that just 5% of recyclable materials are turned into new things.

The Daily spoke with Coile about his scientific research, processes and potential impact of his work. 

This interview has been lightly edited for clarity and brevity.

The Daily: Why did you decide to go into research? Could you describe your current research?

Coile: I’ve always been interested in understanding how things work (on) the practical side of things through science and engineering. I worked at Argonne National Lab, just outside Chicago, for two summers before starting my Ph.D. at Northwestern.

Sometimes, I’ll just say my research is working to make mattresses recyclable, but my research is a very specific part of this. Specifically, my research is building and developing kinetic models that track polymer structure. This lets us understand the influence of this structure on the chemical reactions that occur when reprocessing these materials. 

The Daily: How do your research goals impact your typical workday? 

Coile: My day-to-day work varies considerably. Often, there is not a readily adaptable model for the polymer system of interest because kMC is not widely used in studying depolymerization. So some day-to-day work includes model development.

We also need kinetic parameters for our models. Sometimes these can be found in literature, either directly or from using correlations. When not available in literature, we can calculate (the parameters) from quantum chemistry using a technique known as density functional theory. Alternatively, we can fit these parameters to the data. A typical workday may also include analyzing the predictions that the model makes and comparing them to any experimental data that we have.

The Daily: All of these reactions are done on a computer, correct? 

Coile: That is correct. However, we do have experimental collaborators who run experiments. Here at Northwestern, the Torkelson group studies polyurethanes, recycling and reprocess stability. They’ll take these polyurethane materials, chop them up and put them in a press at an elevated temperature and re-mold the material into a new shape. So there is experimental data being generated. And when we want additional data, we can ask.

The Daily: What are polyurethanes?

Coile: They’re the sixth-most produced class of polymers (or plastics). Generally, they’ll be found in your foam mattresses, your shoe soles or building insulation. Polyurethanes are not currently recycled — except for mechanical shredding for carpet underlayment — partly because they’re typically network polymers that can’t be melted.

If you have long chains, you can usually melt the material down. But, in the case of the polyurethane network, it will decompose before it reaches the melting (phase) or before those bonds are all reversible. So you get back to monomers. 

Part of my work is helping to develop polymers, which you can then degrade at the end of life and get something valuable back — whether that’s the original polymer or whether that’s some other useful chemical. But, you can’t have your polymer instantly degrade under operating conditions, because you don’t want your mattress to just turn into a liquid monomer soup. 

The Daily: What’s the biggest challenge in your research?

Coile: I would say physical effects. My research is looking at chemical reaction kinetics and reaction rates, but it’s hard to know how much of that is intrinsic reaction kinetics, and how much of that is physical effects — for instance, crystallinity, mass transport limitations or heat transport limitations. 

When I’m comparing our models to experimental data, there are all these real physical effects that also play a role. So I would say the biggest challenge to the research I do is physical effects and untangling those from reaction kinetics.

The Daily: What excites you most about the work you are doing?

Coile: The potential scale of the impact of this research. The amount of plastic we produce every year is tremendous. There’s a lot of plastic waste, and polyurethanes are some of the largest contributors to that. Even a small recovery of value or the potential to eliminate waste motivates me to work on these problems.

Email: [email protected]

Twitter: @noracollins02

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