Efficient nickel-catalysed telomerisation on glycerol carbonate: a new linker route for lignin functionalisation

An effective method of grafting functionalities onto lignin based on glycerol carbonate has been developed. This biobased grafting reagent reacts with lignin without generating co-products. Alkenyl groups were added to the glycerol carbonate moiety from 1,3-butadiene chemistry using the nickel-catalysed hydroalkoxylation reaction and the newly developed nickel-catalysed telomerisation reaction under solvent-free conditions. The high-atom economical reactions lead to three different sets of glycerol carbonate ethers with various chain lengths that can be separated from the catalyst to avoid lignin contamination with metals. Kraft, organosolv and soda lignins, without prior purification, were grafted via ether functions using these linkers in a clean and efficient procedure. The technical and modified lignins were characterised by NMR, IR and SEC, and their thermal properties were determined by DSC. The glass transition temperatures of the modified lignins are significantly reduced, opening up possibilities of shaping, for example, on hot presses. In addition, these modifications offer the possibility of inserting new reactive functions within the lignin, including unsaturations and alcohols, allowing a new range of lignin-based resins to be developed. An effective method of grafting functionalities onto lignin based on glycerol carbonate has been developed using an efficient nickel-catalysed telomerisation reaction.

Automated summary

An effective method of grafting functionalities onto lignin based on glycerol carbonate has been developed using an efficient nickel-catalysed telomerisation reaction. This method allows lignin to have new reactive functions and reduces the glass transition temperatures of modified lignins, thereby expanding the application range of lignin-based resins.