Poly(ethylene glycol) diisopropenyl ether for lignin-based reversible acetal networks: towards acid-resistant and environmentally friendly thermosets

A novel family of lignin-based thermosets that rely on acetal linkages and does not release hazardous compounds during degradation is proposed as future material, circular by design. Poly(ethylene glycol) diisopropenyl ether (PDIP) was utilized as a soft segment to form the acetal linkage with the lignin hydroxyl groups via “click” reaction. The use of PDIP instead of previously utilized poly(ethylene glycol) divinyl ether (PDV) prevents the release of harmful acetaldehyde during the acidic hydrolysis of the materials. In addition to the lower toxicity of the degradation products, thermosets with PDIP are more resistant to acidic hydrolysis than those with PDV. Characterization of the thermosets by thermal analysis revealed that the merits of this new lignin-PDIP thermoset extended to increased thermal stability, with Td5%, Td30% and Ts values of 253, 349 and 152 °C, respectively. The ease of synthesis and high yields achieved encourage further work to develop circular materials solutions based on lignin and PDIP.