Synthesis and properties of novel self-catalytic phthalonitrile monomers with aliphatic chain and their copolymerization with multi-functional fluorene-based benzoxazine monomers

Abstract

A novel series of self-catalytic phthalonitrile monomers with aliphatic segments (BPAA) were synthesized via nitro nucleophilic substitution reaction of bisphenol compound and 4-nitrophthalonitrile. Bisphenol compound was reductant with secondary amine groups of Schiff base derived from the reaction of vanillin and one of the aliphatic diamine such as 1,2-ethylenediamine, 1,3-propane diamine, and 1,6-hexamethylenediamine. The curing reaction of BPAA monomers can be carried out without any catalyst. BPAA monomers showed excellent processing properties. Moreover, BPAA polymers (poly(BAPP)) showed superior thermal stabilities and higher glass-transition temperatures (Tg) (302–317 °C). The 5% thermal decomposition temperatures (T5) of poly(BAPP) and char yield (Yc) at 800 °C under nitrogen atmosphere were 352.5–410.5 °C and 61.3–66.8%, respectively. To further improve the thermal stability of poly(BAPP), BPAA monomers were modified by multi-functional fluorene-based benzoxazine monomers (MFFB) due to their excellent reaction activities. The results showed that BAPP/MFFB systems had high reaction activities and good processing behaviors. The similar thermal stabilities between BAPP and MFFB can give stable and excellent thermal stability (T5 ≥ 378 °C) to the poly(BAPP/MFFB) systems.