A New Approach for Designing Biodegradable Plastics

Plastics are a part of everyday life, found in products ranging from bottles and food packaging to polyester fibers. Many of these products are made from polyethylene terephthalate (PET), a petroleum-based plastic used for its durability and resistance to heat and water. However, those same properties and its tightly organized molecular structure makes it resistant to degradation. As a result, PET can persist in the environment for long periods of time.

In a recent article, MIT researchers Natalie Mamrol, a former graduate student in the Department of Chemical Engineering’s Rutledge Research Group; Phoebe Weil, a former undergraduate researcher in the Rutledge Research Group; Katharina Fransen,  a former graduate student in the Department of Chemical Engineering’s Olsen Research Group; Gabrielle Godbille-Cardona and Alex Zappi, graduate students in the Olsen Research Group; Gregory Rutledge, the Lammot du Pont Professor of Chemical Engineering; and Bradley Olsen, the Alexander and I. Michael Kasser Professor of Chemical Engineering, explores a potential solution to the environmental challenges associated with PET.

The researchers investigated another type of plastic called furanoate polyesters, which are made using a chemical called FDCA and can be produced from biological/renewable sources. 

The challenge is making the plastic work well for bottles, packaging, and fibers. To have useful mechanical and thermal properties, the molecules need to be arranged in a partially crystalline structure, called semi-crystalline. In contrast, amorphous plastics have a more disorganized molecular structure, which gives them different properties and can make them easier for biological processes to break down. 

Furanoate plastics can be either semi-crystalline or amorphous, so researchers worked to develop a plastic that is just crystalline enough to be strong and useful while still being biodegradable.

They took several of these furanoate plastics and copolymerized them with small amounts of other types of molecules. The hope was that these little changes might make the material easier for microorganisms to break down, without completely destroying the organized/crystalline structure that makes it useful. Using high-throughput techniques, they created over 200 unique furanoate copolyester chemistries.

Most notably, two furanoate copolyester compositions, both copolyesters of poly(ethylene furanoate), stood out as the most promising candidates based on their crystallinity of over 20% and biodegradability. These offer promising pathways for advancing the development of bio-based plastics.

This research was catalyzed by an MCSC Seed Award that supported the team’s exploration of more sustainable alternatives to traditional polyester for textiles. 

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