Application of Furan-Based Dicarboxylic Acids in Bio-Derived Dimethacrylate Resins

Two renewable dicarboxylic acids, furan-2,5-dicarboxylic acid and 2,2′-bifuran-5,5′-dicarboxylic acid, were applied as bisphenol A substitutes to prepare partially bio-based dimethacrylate resins. The furan-based dimethacrylates were synthesized using their diglycidyl esters as intermediates, which were then reacted with methacrylic acid. This reaction was found to give isomeric mixtures, where the formed methacrylate end group had three different configurations as elucidated using one-dimensional (1D) and two-dimensional (2D) NMR. The ratio between the different end groups could be controlled to an extent by using 1,1,1,3,3,3-hexafluoroisopropanol as the sole reagent to facilitate a reaction between the furan diglycidyl esters and methacrylic acid. The control over the configuration of the methacrylate end group is demonstrated to be a possible tool to influence the properties of the resultant dimethacrylate monomer and the cured resin. The bifuran dimethacrylates were found to have viscosities of ca. 110–120 Pa·s at 25 °C, while the furan dimethacrylate had a viscosity of about 40 Pa·s at 25 °C. It is demonstrated that by diluting the furan-based dimethacrylates with 40 wt % of methacrylated eugenol, a bio-based reactive diluent, the liquid resins could be cured into thermosets with glass-transition temperatures of 177–209 °C and 5% mass loss temperatures of 359–375 °C under a nitrogen atmosphere.