Vanillin- and Isovanillin-Based Phthalonitrile Resins Containing Spirocycle Acetal Structures

Preparing biobased high-performance thermosetting resins is one of the most important factors for sustainable development. In this work, two kinds of phthalonitrile resins containing spirocycle acetal structures were synthesized from pentaerythritol and renewable vanillin and isovanillin by an efficient two-step process. The structures of vanillin- and isovanillin-based phthalonitrile (VPN and IVPN) monomers were characterized by Fourier transform infrared (FTIR), NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and elemental analysis. The curing behaviors of these monomers were studied by differential scanning calorimetry and FTIR. The thermal stability and dynamic mechanical properties of the cured resins were investigated by thermogravimetric analysis and dynamic mechanical thermal analysis. The processing properties were studied by a rheological analysis. Compared with traditional petroleum-based phthalonitrile resins such as bisphenol A and bisphenol, cured VPN and IVPN resins exhibited good thermal stability and thermomechanical properties, high glass transition temperature (Tg), and excellent processability.