Synthesis and characterization of a linear CARDO polyimide from (5,5′-bisisobenzofuran)-1,1′,3,3′-tetrone and 4,4′-(9 H-fluoren-9-ylidene)bisphenylamine

Abstract

Starting from an aromatic diamine, 4,4′-(9 H-fluoren-9-ylidene)bisphenylamine (FBPA), we have synthesized a series of linear polyimides by polycondensation with different molar proportions of (5,5′-bisisobenzofuran)-1,1′,3,3′-tetrone (BTDA). The polymers were anhydride end-capped or phenylimide end-capped. Owing to the presence of lateral fluorene groups (CARDO structure), the fully cyclized FBPA/BTDA polyimides exhibited good solubility in many solvents such as N, N-dimethylformamide, N-methylpyrrolidone, m-cresol, dimethylsulphoxide and N, N-dimethylacetamide. A detailed study of the FBPA/BTDA chemical structure and molecular weight was performed by 13C nuclear magnetic resonance and size exclusion chromatography. The thermal and mechanical properties of polymer films were then investigated. The glass transition temperature determined from thermomechanical analysis ranged from 350 to 380°C and the Young's modulus measured from tensile tests was about 2.5 GPa at room temperature and 1.7 GPa at 200°C. Thermogravimetric analyses and water uptake determination showed the high decomposition temperature, near to 400°C under argon, and the low water absorption (lower than 1 wt%) of the FBPA/BTDA polyimides.