Biobased and Aromatic Reversible Thermoset Networks from Condensed Tannins via the Diels−Alder Reaction

Thermo-reversible networks were obtained for the first time from tannins, an aromatic biobased polyphenol, by reacting furan-bearing tannins and telechelic oligomers with maleimide end groups, using the Diels−Alder (DA) reaction. Condensed tannins from mimosa (Acacia mearnsii) were functionalized with furfuryl glycidyl ether and thoroughly characterized by 1H, 31P NMR, and FTIR spectroscopy. The accessibility of the grafted furan groups was confirmed by a model reaction with N-methylmaleimide. Different cross-linked networks were then obtained by DA reaction with three PPO and PPO-b-PEO-b-PPO oligomers and evidenced by FTIR spectroscopy. The thermal properties of the obtained networks were evaluated with differential scanning calorimetry (DSC) and thermogravimetric analysis. Then, the reversibility of the cross-linking was shown by a quick return to the liquid state upon heating at 120 °C. The retro Diels−Alder reaction was studied by size exclusion chromatography and DSC.