Paper outlines catalytic process to make eco-friendly plastics from natural polymer

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A new study led by Colorado State University Distinguished Professor Eugene Chen outlines a path to creating advanced, recyclable plastics. Published in Nature, the study describes a breakthrough method for upconverting a natural polymer that is usually made by microorganisms into a wide range of new and more sustainable high-performance materials as well as valuable chiral small molecules for organic and polymer synthesis.  

The method is an important step toward a circular materials economy in which products are designed to be bio-based, reused, repurposed or recycled rather than ending up in landfills – greatly reducing the burden of chemicals and plastics on the environment. 

The study centers on innovative utilization of poly(3-hydroxybutyrate) or P3HB — a biodegradable polyester produced by microbes. P3HB belongs to a family of materials called polyhydroxyalkanoates (PHAs), which can be redesigned to perform similarly to petroleum-based plastics but with one key advantage: They can break down naturally in soil and oceans.  

Although researchers have explored modifying PHAs before, the potential has been limited because only one version of the macromolecule is found in nature. That natural form comes with fixed traits, such as a specific melting temperature, strength and flexibility. To address this, Chen’s team developed a catalytic process that changes the molecule’s “handedness.” 

In chemistry, that term refers to enantiomers – molecules that are mirror images of each other, like your left and right hands. Just like a left shoe won’t fit your right foot, the two forms of a molecule can behave very differently. When enantiomeric molecules are covalently linked to form a macromolecule or a polymer, many different versions of PHAs can then be produced.  

By unlocking these different versions — and related 3D forms known as stereoisomers — Chen’s team has opened the door to a new generation of customizable materials with properties tailored for different applications. For example, one version of a new macromolecule could provide extra flexibility while another could provide high dimensional rigidity for totally different applications.  

“The new PHA polymers  we have unlocked using natural P3HB as the starting material exhibit improved properties for potential use in packaging, medical products or adhesives,” Chen said. “They can also be chemically broken down and recycled into smaller chiral molecules with specific three-dimensional shapes that are useful in making medicines, new plastics and other valuable compounds.” 

This work builds on years of research in Chen’s group on understanding and improving P3HB performance properties as a versatile biodegradable material. In earlier work published in Science, his team showed that by changing the microstructure of synthetic P3HB, they could make it stick to surfaces more strongly than commercial superglues. The current study flips the approach: Instead of making synthetic P3HB from scratch, the team starts with natural P3HB and catalytically transforms it into new PHA materials with enhanced performance and recyclability.  

Chen is part of the Department of Chemistry in CSU’s College of Natural Sciences. The study was supported by the U.S. Department of Energy’s Basic Energy Science – Catalysis Science program, and by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, Advanced Materials and Manufacturing Technologies Office (AMMTO) and the Bioenergy Technologies Office (BETO), which fund the BOTTLE Consortium. The paper includes contributions from co-first authors Jun-Jie Tian and Ruirui Li along with six other CSU researchers in Chen’s lab.