Synthesis of new diacid monomers and poly(amide-imide)s: study of structure-property relationship and applications

Two diimide-diacid monomers 4,4'-bis[4 ''-(trimellitimido)phenyl isopropylidene-4'"-phenoxy]diphenyl sulfone and 4,4'-bis[4 ''-(trimellitimido)phenylisopropylidene-4'"-phenoxy] were synthesized. The structures of the monomers were characterized by FT-IR and H-1-NMR spectroscopy. A series of novel poly(amide-imide)s were prepared from this two diacids and aromatic diamines through phosphorylation reaction. The PAIs were characterized by FT-IR, H-1-NMR, XRD, TGA, and DSC, solution viscosity, solubility test and electrical properties. Poly(amide-imide)s showed excellent solubility due to the presence of flexible groups and isopropylidene unit in the polymer backbone. They also exhibited good thermal stability and the temperatures at which 10% weight loss occurred in the range 385-465 degrees C. These PAIs found to have a dielectric constant in the range 3.25-4.20 at 10 kHz and have excellent electrical insulation character and can be used as insulation materials for electrical items operating at elevated temperatures.