Breakthrough Polymer Could Lead to Endlessly Recyclable Plastics

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IBM Research Scientist Jamie Garcia, who MIT recently named a 2015 “Innovator Under 35” for her work in polymers, recently told an EmTech audience how her “chance discovery sparked a quest for plastics that are both strong and recyclable.” The chemistry PhD hopes that the properties of these new polymers lead to longer-lasting, more-durable, even endlessly recyclable plastics. THINK caught up with Garcia recently to ask her about her work and how “self-healing” paint could be one of the first products to take advantage of these new-found properties.

THINK: What’s the biggest misconception about plastic that you come across?

Jamie Garcia: I think people generally think of plastic as being cheap materials. Or that plastic is just good for making toys (which break easily), those soda can rings (that sea life gets trapped in), or bottles (that leach chemicals).

What people don’t realize is that we use plastic for so many other things, by dialing into properties based on its chemical composition. For example, we can make plastic electrically conductive (like OLEDs), antimicrobial (think disposable medical devices), or lightweight and strong (such as composites in the tail of Boeing 787s). So, plastic is an essential contributor to the quality of our lives and to our new and future technology; it helps us save on fuel and reduce CO2 emissions; it can even help prevent disease.

THINK: Why is plastic recycling limited (to the typical 3-4 times)?

JG: Recycling’s is limited because plastic’s mechanical properties degrade each time it’s melted down and remolded. For example, it can lose its flexibility and become brittle, become hazy instead of transparent, and can become discolored (yellowing, for example). Once the mechanical or optical properties are altered the plastic is no longer suitable to be used for its original purpose, so it has to be re-purposed.

The endlessly recyclable and self-healing polymer

THINK: Your breakthrough makes plastics, even previously un-recyclable plastics, recyclable hundreds of times over. What was unique about the thermoset you were using that gave it this incredibly flexible power when added to acid?

JG: The crosslinking chemical motif, the part that makes this polymer a strong network, has a special property that allows it to be hydrolyzed (the breakdown of a compound by chemical reaction with water) only at very low pH (pH ~ 0). We used computational chemistry alongside experiments to help guide us to the best synthetic method to make these materials, including cure conditions (this is absolutely critical!) and choice of monomer (also critical!) to access materials with the best properties. Usually you don’t get both properties in one material: this thermoset is both strong and revertible.

THINK: Because of these flexible recycling properties, there is already speculation about your polymer’s self-healing properties for things like paint. How could your polymers be introduced into something like paint?

JG: The self-healing property of some of our materials was a welcomed, but unexpected bonus to studying this chemistry! The reason why it could be used for self-healing paint is that we can make materials that are a blend of the chemical motif that we found that self-heals, along with the chemical structures that paints are made of. We’ve thought of ways this can be accomplished, such as using spreadable, crosslinked structures that remain reactive so that they respond to their environment, making them resistant to cracking, scratching, etc.

The resulting films (paints in this case) you can think of almost like “living,” or “smart” polymers, meaning that it continues to be dynamic and continuously exchange over its lifetime in response to the environment. Due to the chemical structure, if the bonds are broken they can react again to reform bonds, and “heal” the coatings or films.

THINK: Damaged paint makes people think of peeling or chipped exterior walls of a building, or maybe a car – due to age and weather. If these things were painted with your polymers, what conditions would trigger the self-healing properties?

JG: It depends on which structure we’re talking about. In some cases, simple water treatment would heal the film, in other cases you might apply rubbing alcohol or nail polish remover to the crack to heal it. Still other cases might require wiping the crack with vinegar or something similar. It’s feasible that you might not even need to do anything to heal the paint, though. And it might be able to heal on its own. This would be an interesting engineering challenge!

THINK: What is needed on an industrial-sized scale to produce – and recycle – your polymers?

JG: For production, we need access to (already existing) scale-up equipment and perhaps tweak the processing conditions to align with those already implemented. IBM is not a chemical company, so we would need a partner for this next step. To recycle them? That’s a larger challenge. We would need a large-scale plant that would be dedicated to chemical recycling for polymers.

Most polymers are recycled with an inexpensive melt-and-remold approach, so the infrastructure isn’t in place for recycling plastics with chemical methods (yet!). It would likely be a more expensive process. That said, I still think that in the long run it would be worth it – we could recover more of our materials, and implementing chemical recycling for polymers would ultimately save on energy, resources, and landfill space.

Watch Jamie Garcia present “Powerful Plastic” at MIT’s EmTech