Researchers at CSU Discover A New Recyclable Polymer

New “infinitely” recyclable plastic points towards future-generation polymers that not only are chemically recyclable, but also exhibit robust practical properties.

Colorado State University chemists have announced in the journal Science the discovery of a new ‘infinitely’ recyclable polymer, according to a release from the university. Led by Eugene Chen, professor in the department of chemistry, this new polymer can be converted back to its original small-molecule state for complete chemical recyclability. The researchers say that this can be accomplished without the use of toxic chemicals or intensive lab procedures.

The work builds on a previous generation of a chemically recyclable polymer Chen’s lab first demonstrated in 2015. Making the old version required extremely cold conditions that would have limited its industrial potential. The previous polymer also had low heat resistance and molecular weight, and, while plastic-like, was relatively soft.

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But the fundamental knowledge gained from that study was invaluable, Chen said. It led to a design principle for developing future-generation polymers that not only are chemically recyclable, but also exhibit robust practical properties.

The new, much-improved polymer structure resolves the issues of the first-generation material. The monomer can be conveniently polymerized under environmentally friendly, industrially realistic conditions: solvent-free, at room temperature, with just a few minutes of reaction time and only a trace amount of catalyst. The resulting material has a high molecular weight, thermal stability and crystallinity, and mechanical properties that perform very much like a plastic, Chen said. In addition, the polymer can be recycled back to its original, monomeric state under mild lab conditions, using a catalyst. Without need for further purification, the monomer can be re-polymerized, thus establishing what Chen calls a circular materials life cycle.

“The polymers can be chemically recycled and reused, in principle, infinitely,” Chen said.

This new polymer technology has been demonstrated at the academic lab scale so there is still much work to be done to perfect the patent-pending monomer and polymer production processes he and colleagues have invented.

With the help of a seed grant from CSU Ventures, the chemists are optimizing their monomer synthesis process and developing new, even more cost-effective routes to such polymers. They’re also working on scalability issues on their monomer-polymer-monomer recycling setup, while further researching new chemical structures for even better recyclable materials.

“It would be our dream to see this chemically recyclable polymer technology materialize in the marketplace,” Chen said.

The paper’s first author is CSU research scientist Jian-Bo Zhu. Co-authors are graduate students Eli Watson and Jing Tang.