Synthesis of an Epoxy Monomer from Bio-Based 2,5-Furandimethanol and Its Toughening via Diels–Alder Reaction

A bio-based epoxy 2,5-bis[(2-oxiranylmethoxy)methyl]-furan (BOF) has been synthesized from 2,5-furandimethanol and toughened by its Diels–Alder (DA) reaction adduct DA-BOF, which contained a flexible pendant chain. The chemical structures of the synthesized monomers were identified by nuclear magnetic resonance (1H NMR and 13C NMR). The thermal reversibility of DA-BOF was investigated by differential scanning calorimetry and ultraviolet–visible (UV–vis) spectroscopy. On the basis of the UV–vis results, the degree of retro Diels–Alder reaction was determined to be 25–27% in different cured systems. The study of the mechanical properties indicated that when the content of DA-BOF reached 50%, an 85% increase in impact strength could be obtained without seriously sacrificing its tensile strength or modulus. The strategy described in this work could help us to achieve a bio-based epoxy resin with increased impact strength and nearly unaffected tensile properties.