A polymer was discovered that possesses many of the same characteristics as plastics, such as light weight, heat resistance, strength, and durability. But the new polymer, unlike typical petroleum plastics, can be converted back to its original small-molecule state for complete chemical recyclability. This can be accomplished without the use of toxic chemicals or intensive lab procedures.
Polymers are a broad class of materials characterized by long chains of chemically bonded, repeating molecular units called monomers. Synthetic polymers today include plastics as well as fibers, ceramics, rubbers, coatings, and many other commercial products.
The work builds on a previous generation of chemically recyclable polymer that was made using 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. The work led to a design principle for developing future-generation polymers that not only are chemically recyclable, but also exhibit robust practical properties.
The new 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. Most importantly, 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 a circular materials lifecycle.
New green plastics, rather than surviving in landfills and oceans for millions of years, could be simply placed in a reactor and, in chemical parlance, de-polymerized to recover their value — not possible for today's petroleum plastics. Back at its chemical starting point, the material could be used over and over again, completely redefining what it means to “recycle.”
The new polymer technology has only been demonstrated at the academic lab scale. Researchers are optimizing the monomer synthesis process and developing new, even more cost-effective routes to such polymers. They are also working on scalability issues on the monomer-polymer-monomer recycling setup, while further researching new chemical structures.