In search for plant-derived glues via the CHEM21 toolkit

Within the GREEN-CHEM network, Ghent university researchers from the Polymer Chemistry Research Group led by Professor Filip Du Prez, have applied the ‘CHEM21’ evaluation toolkit to improve the sustainability of some synthetic procedures, i.e. to produce renewable building blocks for adhesives. The building blocks were derived from the essential oils of plants via a more sustainable reaction procedure producing less waste than conventional methods.

Green alternative

The renewable building blocks produced in this research are acrylic monomers derived from terpenoids, a subclass of the broader, naturally produced terpenes. These terpene compounds can be extracted from the essential oils of various plants such as citronella oil from geraniums and lemon grass. Terpenes offer versatile functionalization possibilities when incorporated in synthetic polymers because of their structural diversity. Prof. Du Prez: “These building blocks can then be incorporated in adhesives, such as glues, to answer the need of the adhesives industry for more biobased alternative to the current crude oil-based counterparts.”

The research team screened different synthetic methods to synthesize a range of terpenoid-based (meth)acrylates via standard and less conventional methods using the CHEM21 green metrics toolkit. “This allowed us to come up with a more sustainable reaction procedure, producing less waste then conventional methods”, explains prof. Du Prez.

 A principled toolkit

The used evaluation method was originally developed in 2015 by a consortium led by prof. James Clark, another member of the GREEN-CHEM network. It was named the “CHEM21 green metrics toolkit”, and can be seen as an extension to the ’12 principles of green chemistry’. This is a set of principles to guide the practice of green chemistry by addressing a range of ways to reduce the environmental and health impacts of chemical production. They also indicate research priorities for the development of green chemistry technologies.

 Sustainability evaluation

The toolkit combines simple standard metrics with more comprehensive ones to cover all sustainability aspects, including upstream and downstream steps often not considered before. Moreover, a new flag system indicates the ‘greenness’ of a certain parameter, such as energy input, catalyst use, recycling and abundance. “This ensures a truly holistic approach to assess sustainability based on a series of key parameters with both qualitative and quantitative criteria to determine how green a reaction is”, says prof. Du Prez.

“With this study, we wanted to prove the ease of this evaluation system and encourage a more widespread use of this toolkit! Used not only in polymer science, but also in other areas of chemistry”, concludes prof. Du Prez. The CHEM21 green metrics toolkit can thus be seen as a huge leap forward for the green chemistry community, using less arbitrary and more comparable methods to evaluate the greenness of a reaction, which is something we can all greatly benefit from.