Power to the polymers: Researchers devise sugar-based plastic with food-grade potential

18 Mar 2022 --- University of Birmingham, UK, and Duke University, US, researchers have discovered “exceptional” strength and toughness in novel polymers made from sugars, which have the potential for food-grade application. The study is published in Angew Chemie.

Duke University professor Dr. Matthew Becker tells PackagingInsights: “While it is early in the evolutionary lifetime of these materials, the properties of the polymers are unique.”

The study examined two polymers based on isosorbide and isomannide produced by a recently disclosed method that uses sugars as a starting point for synthesis. Both polymers have superior properties to conventional thermoplastic elastomers, and in addition, are degradable and mechanically recyclable. 

In a key finding, the researchers discovered that the polymer made from isosorbide displayed superior elastic recovery and toughness, which was shown to be a result of the stereochemistry of the sugar groups in the materials.

Topping existing efforts
Becker explains the mechanical and optical properties “far exceed” what is seen in most environmentally sustainable polymers, where properties remain far below existing performance requirements.

“This has been a big problem in the field where industries are unlikely to yield on performance characteristics.”Both polymers have superior properties to conventional thermoplastic elastomers and are degradable and mechanically recyclable. 

“Food-grade packaging is certainly a possibility and we are looking into the barrier properties of the materials,” he adds.

Using computer simulations and other experimental techniques, the researchers showed that the difference in elastic recovery results from the way the sugar stereochemistry directs the network of hydrogen bonds between and within the long-chain molecules. 

Becker says the biggest challenge was determining the origin of the unique properties. “It turns out this was stereochemistry directed hydrogen bonding. Individually, these bonds are weak but collectively, especially when oriented, they are exceptionally strong. The modeling by our colleague Andrey Dobrynin of UNC Chapel Hill was key to providing insight and support to our experimental measurements,” he explains.

The researchers concluded that both polymers have high optical clarity, exceptional mechanical strength and extensibility, but the isosorbide-based polymer has superior toughness due to its higher elasticity.

Stereochemistry as a design element
Meanwhile, Professor Andrew Dove from Birmingham’s School of Chemistry, who led the research, says that the long-term impacts of modern polymers on the environment are a significant concern.

“Isosorbide is a renewable feedstock alternative to petroleum derivatives for commercial polymer production. It is derived from plants, and, as one of the top 20 biomass sourced molecules, is available at a scale that is consistent with commercial production of bioplastics,” he explains.

Becker adds: “Most bio-sourced plastics have lacked the mechanical properties needed to compete in commercial applications and lose nearly all of their mechanical properties when reprocessed. The materials outlined in this paper change that paradigm.”Becker says the sugar-based polymers’ mechanical and optical properties “far exceed” what is seen in most polymers to date.

Sustainable feedstocks
The researchers have also demonstrated that the reported properties are possible using sustainably sourced feedstocks.

“Dr. Dove and I both believe that the use of stereochemistry as a design element is the most important finding in this work and our efforts will continue to advance this new approach in multiple technology applications,” continues Becker.

“This will result in additional materials with properties exceeding what we have already reported.”

“As far as cost, we expect the supply chains to evolve and mature as the materials advance in commercial potential. They will not be at commodity prices to start but the cost will come down with time. This is true of almost all materials regardless of market sector.”

A joint patent application has been filed by the University of Birmingham Enterprise and Duke University, covering both the polymers, and the method of making them. The researchers are now looking for industrial partners who are interested in licensing the technology.

By Natalie Schwertheim