A team of scientists at Colorado State University (CSU) has successfully produced a completely recyclable, biodegradable polymer.

“More than 200 pounds of synthetic polymers are consumed per person each year – plastics probably the most in terms of production volume. And most of these polymers are not biorenewable,” said Prof. Eugene Chen of CSU’s Department of Chemistry.

“The big drive now is to produce biorenewable and biodegradable polymers or plastics. That is, however, only one part of the solution, as biodegradable polymers are not necessarily recyclable, in terms of feedstock recycling.”

Writing in the journal Nature Chemistry, Prof. Chen and his colleague, Miao Hong, describe synthesizing a polymer that, when reheated for about an hour, converts back to its original molecular state, ready for reuse.

Their starting feedstock was gamma-butyrolactone (GBL), a monomer that scientists had declared non-polymerizable.

Prof. Chen and Ms Hong used both metal-based and metal-free catalysts to synthesize the polymer, called poly(GBL).

They employed specifically designed reaction conditions, including low temperature, to make the poly(GBL), and heat between 428 – 572 degrees Fahrenheit (220 – 300 degrees Celsius) to convert the polymer back into the original monomer, GBL, demonstrating the thermal recyclability of the polymer.

“This work established relationships between the poly(GBL) structure and its thermal and dynamic mechanical properties, and it demonstrated the complete thermal recyclability of poly(GBL) back into its monomer, which thereby opens up unique opportunities for discovering new sustainable (renewable and recyclable) biomaterials based on the ROP (ring-opening polymerization) of other five-membered lactones,” Prof. Chen and Ms Hong said.

Their discovery has promising market potential, and a provisional patent has been filed with the help of CSU Ventures.

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Miao Hong & Eugene Y.-X. Chen. 2016. Completely recyclable biopolymers with linear and cyclic topologies via ring-opening polymerization of γ-butyrolactone. Nature Chemistry 8, 42-49; doi: 10.1038/nchem.2391