Preparation and characterization of thermo-processable poly(benzimidazole imide)s with soluble and high heat-resistance containing N-phenyl-benzimidazole

In this paper, we present a synthetic strategy for N-phenyl substituted benzimidazole-derived diamines, including 2-(4-(4-aminophenoxy) phenyl)-1-phenyl-1H-benzo[d]imidazol-5-amine (para-diamine) and 2-(3-(4-aminophenoxy) phenyl)-1-phenyl-1H-benzo[d]imidazol-5-amine (meta-diamine). Two distinct series of N-phenyl substituted poly (benzimidazole imide)s (PBIPIs) were synthesized via reaction with different aromatic dianhydrides. The simulation reveals distinct amine reaction activities of two diamine monomers. The obtained PBIPIs exhibit exceptional heat resistance attributed to N-phenyl substituted benzimidazole (BI). The temperature at which weight loss of 5 % (T5%) is in the range of 491–595 °C under N2 environment, while the glass transition temperature is 237–329 °C. The PBIPIs exhibit specific solubility characteristics due to the flexible ether linkage groups' non-coplanarity and bulky pendant benzene groups. The PBIPIs possess tensile strength between 108 and 142 MPa, a tensile modulus of 4.0–5.9 GPa, and an elongation at a break of 4.2–26.4 %, indicating excellent mechanical properties. Additionally, the PBIPI with controlled molecular weight generated from BPADA incorporating 2-(3-(4-aminophenoxy) phenyl)-1-phenyl-1H-benzo[d]imidazol-5-amine (B-BPADA-PA) demonstrates exceptional melt processability. B-BPADA-PA possesses remarkable melt stability since its minimum complex viscosity is only 2100 Pa∙s at 400 °C, and its melt viscosity ratio is 1.34 at 380 °C.