Diisocyanates are used in the preparation of all polyurethanes, ranging from the foams used in shoe soles to the thermoplastics used in cell phone cases.

Aromatic diisocyanates, which give polyurethane foams their structure, are commonly prepared on the megaton scale in highly secure facilities due to the use of phosgene, a highly reactive and toxic chemical reagent.

In Angewandte Chemie International Edition, Michael Burkart’s lab at UC San Diego reports the preparation of fully bio-based aromatic diisocyanates from a simple monosaccharide, D-galactose.

“This method provides a new route to 100% bio-based polyurethane foams, achieving a long-standing goal for the industry,” says Burkart.

This new route avoids the use of transition metals, gaseous reagents or any high-pressure/temperature reactions. As an application, the team demonstrates the synthesis of a thermoplastic polyurethane (TPU) using these renewable diisocyanates, which show excellent material properties equivalent to petroleum-based TPUs.

These materials can serve as drop-in replacements for existing polyurethanes, which can now be sourced from 100% bio-based materials. Next, the team is developing scale-up procedures to prepare them in kilogram quantities for prototype applications.