Phthalonitrile resins based on biomass vanillin with high storage modulus and good processing window

Bio-based phthalonitrile resins were synthesized using a two-step process. Initially, vanillin underwent a nucleophilic reaction with nitro and potassium carbonate to form intermediates, which were then dissolved in N, N-dimethylformamide. The intermediate was divided into two portions, with 4,4’-oxydianiline and 4,4’-methylenedianiline added to each portion, respectively, to produce two different vanillin-based phthalonitrile monomers: OVA monomer and DVA monomer. The successful synthesis of these two bio-based phthalonitrile monomers was confirmed using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Differential scanning calorimetry was employed to study the processability of the monomers, revealing that OVA monomer and DVA monomer had a wide processing window of 110°C and 69°C, respectively, which were advantageous for resin processing. Dynamic mechanical analysis showed that the storage modulus of the OVA and DVA resins reached 4818 MPa and 3526 MPa, respectively, with a 24-h water absorption rate of only 1.03% and 0.90%. This study presents a viable method for synthesizing bio-based phthalonitrile resins, which can be widely utilized as functional and structural materials in daily life due to their renewability, degradability, and minimal environmental impact.