Reducing the melting point and curing temperature of aromatic cyano-based resins simultaneously through a Brønsted acid-base synergistic strategy

High melting points (M p ) and high curing temperatures are two key processing problems that limit the application of aromatic cyano-based (AC) resins. A Brønsted acid-base synergistic strategy based on an acid-base eutectic and mechanisms for nucleophilic addition and ionization equilibrium are proposed to reduce the M p and curing temperature of AC resins. Blends of 4,5-dicyanoimidazole (DCI, Brønsted acid) and amine-containing phthalonitriles (4‐(4 or 2 or 3)‐aminophenoxy) phthalonitrile, APNs, Brønsted bases) were selected as model acid-base systems to study the synergistic behaviors in processing. The results show that the M p and the peak exothermic temperature (T rp ) of APN-DCI blends can be reduced by more than 31 °C and 85 °C compared with their intrinsic components, respectively. DSC and XRD show that the decrease in the Mp of the blends is induced by the formation of eutectics. A positive relationship between △pKa and the curing reactivity is confirmed by theory and experimental methods. The cured products show outstanding thermal and mechanical properties compared with reported AC resins. This research provides a new convenient route for regulating the curing behavior of AC resins and will significantly promote the development of high-performance AC resins. • The presented paper has the following highlights: • A Brønsted acid-base synergistic strategy was proposed to improve processability of aromatic cyano-based resins. • A class of aromatic cyano-based resin blends with both low melting point and low curing temperature was reported. • The relationship between △PKa and curing temperature is discussed.