New renewable building blocks for step growth polymers

Researchers from the GREEN-CHEM network at Ghent University and Maastricht University have developed biobased monomers as renewable building blocks for step growth polymers (a long chain of building blocks). These polymers are used for a broad range of applications, ranging from packaging, clothing, and electronics to materials for construction and more. The resulting polymers are up to 100% renewable and show thermal and mechanical properties that are comparable to traditional crude oil-based polymers (plastics) currently on the market.

The team of prof. Filip Du Prez at Ghent University has developed new renewable building blocks in close collaboration with professor Stefaan De Wildeman from Maastricht University. The new building blocks are used in so-called step growth polymers (such as polyesters, polycarbonates, and polyurethanes), which are used for a broad range of applications ranging from packaging, clothing, and electronics to materials for construction and many other applications.

These polymers are known for their good mechanical properties and their thermal stability. Often, rigid, non-flexible building blocks are combined into very long chains, the polymers. This leads to a desirable combination of high mechanical strength at temperatures up to 150 °C and ductility. The researchers ensured the necessary rigidity of the building block by synthesizing cyclic structures.

Switch to renewable resources

There are many good reasons to switch to renewable resources to get a more sustainable chemistry. “However, one aspect that is often overlooked is the more hidden footprint in transporting the raw materials”, says prof. De Wildeman. “The raw materials we use, like glycerol and fermentation products of carbohydrates, can be produced from local biomass everywhere around the globe.” This can further reduce the carbon footprint of these polymers compared to traditional crude oil-based polymers.

Drop-in solution

“We were able to make new building blocks for polymers by combining glycerol, which is a waste product of the biodiesel production, with cyclohexanedione, which can be obtained from fermentation products of carbohydrates”, says prof. Du Prez. By combining glycerol and cyclohexanedione, the researchers obtained so-called diol monomers which are used for a vast variety of step growth polymers. They were able to show that their monomers can be used in different polymerization procedures that are applied in industry to make the desired materials. “This can make the industrial uptake of these monomers by a so-called drop-in solution much easier”, states prof. Du Prez.

The acetal unit is the base for cyclic structures which provide the necessary stability to the materials. Also, acetal is a functional group that can be easily derived from very abundant types of biomass. For example, carbohydrates can be used, such as cellulose and starch from corn.  “Although acetals are not often used for man-made polymers, it is one of the most abundant functional groups in nature. In fact, carbohydrates themselves are polymers based on the acetal functional group", explains Du Prez.

Prof. Du Prez: "Currently we are working on exploring acetal based monomers further. We will focus on a more detailed understanding of the structure property relationship of the materials. We will also work on lowering the cost of production, since these are key prerequisites before we can start to commercialize these molecules."

Prof. Du Prez and his team will further explore the potential of renewable acetal monomers in close collaboration with prof. De Wildeman. Potential academic or industrial partners that are interested to collaborate are welcome to contact them.