Biopolymers from wood-based lignin in development

(27-09-2017) The GREEN-CHEM network at Karlsruhe Institute of Technology (KIT, Germany) developed a new eco-friendly synthetic pathway to synthesize biopolymers.

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Researchers from the GREEN-CHEM network at the Karlsruhe Institute of Technology (KIT, Germany) developed a new eco-friendly synthetic pathway to synthesize biopolymers starting from the wood component lignin. In combination with different plant oils as a second renewable resource, material properties could be varied from soft to stiff. Thus, fossil-based polymers in various fields can be replaced in the nearby future.

The GREEN-CHEM researchers at KIT showed in several experiments that wood-based lignin, a highly available renewable resource, can replace bisphenol A (BPA), a conventional, petro-based, toxic monomer used in various polymers. These polymers are large molecules that are composed of many identical subunits, the monomers and have a broad range of properties. Therefore, they play an essential and ubiquitous role in everyday life. For example, BPA is used in adhesives, coatings, electronic equipment, food packaging and containers.

Tunable properties lead to various ‘green’ applications

Prof. Michael Meier and his team in Karlsruhe modified the biopolymer lignin using a new methodology that complied with several of the twelve principles of green chemistry, e.g., less hazardous synthesis, use of renewable feedstocks, benign solvents and catalysis.

“Moreover, when we combined the modified lignin with plant oils, another renewable resource with a high availability, we could obtain tunable mechanical product properties depending on the lignin-to-oil ratio and the nature of the oil”, says prof. Meier. The rigid structure of lignin led to stiffer materials, whereas increased plant oil contents led to soft materials. As such, the replacement of petrochemical polymers in a large variety of applications, e.g. in coatings and packaging, seems possible.

Switch to renewable resources

Depleting fossil resources, climate change and a growing demand for energy and chemical products increase the search for renewable alternatives. Therefore, the researchers of the GREEN-CHEM network at KIT aim to design new sustainable synthetic pathways from renewable resources, e.g., wood and plant oils, to replace fossil-based polymers.

“Renewability is not enough”, says prof. Meier, “The field of lignin research is dominated by the use of toxic, conventional reagents. Our aim is to replace these pathways using more sustainable reagents and conditions.”

Why lignin?

Wood consists of three main components cellulose, hemicellulose and lignin, which can be separated via pulping processes. Prof. Michael Meier: “Whereas for cellulose many industrial applications, such as paper production and cellulose-based polymers, are known, only few chemical uses for lignin are described yet.” It can be degraded to obtain aromatics for flavor applications or as antioxidants or it can in theory be used as a biopolymer. However, lignin is a valuable renewable resource that is highly available and not in competition with the food and feed industry.

 Prof. Meier and his team will continue their research on new pathways to more sustainable polymers from lignin as well as other renewable resources. Potential cooperation partners that are interested in this research are welcome to contact them.