Résumé
Poly(furfuryl alcohol) - (PFA) is a biobased thermoset known for its highly crosslinked structure. Bidimensional NMR (2D-NMR) was employed to give new insights on the complex structural organization in PFA with a special emphasis on the side structures resulting from furan ring-opening. Interestingly, the presence of aldehyde functions was for the first time clearly highlighted and quantified in PFA resins. Overall, the aldehydes account for about 20 % of the total carbonyls present in PFA. Results from HSQC and HMBC sequences allowed proposing two pathways for the furan ring opening reactions. The first one is an hydrolytic-ring opening leading to levulinic like species. The second one is rather an oxidative furan-ring opening leading to conjugated aldehydes. These conjugated aldehydes are prone to crosslink via Diel-Alder cycloadditions with furanic entities thus leading to crosslinking. At macroscopic scale, this newly proposed crosslinking pathway would explain the formation of the rigid shell formed at the external surfaces of PFA resins.