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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 1 H-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, 1 H-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°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.

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Two novel aromatic diamine monomers, Bis-4,4′[(4-aminophenyl-2,2′-isopropylidene phenyloxy)] diphenylsulfone and Bis-4,4′[(4-aminophenyl-2,2′-isopropylidene phenyloxy)] benzophenone were synthesized and characterized by IR and 1H-NMR. A series of processable polyimides were prepared by polycondensation of diamines with aromatic dianhydrides. The polyimides were characterized by infrared, 1H-NMR, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, gel-permeation chromatography, solution viscosity and solubility. Polyimides were soluble in polar approtic solvents and increases in solubility in common organic solvents were observed due to the presence of flexible groups and methyl groups in the chain backbone. The polyimides exhibited good thermal stability, and the temperature at which 10% weight loss occurred ranged from 378 to 465 °C in nitrogen. X-ray diffraction measurements revealed that the polyimides were amorphous.

A novel unsymmetrical monomer 5-(4-aminophenoxy)naphthalene-1-amine was prepared from 5-amino1-naphthol and 4-nitrofluorobenzene by the nucleophilic substitution reaction followed by reduction using 'Sn' and HCl. The structure of the monomer was confirmed by FT-IR and 1 H-NMR. A series of aromatic polyimides were successfully prepared from this diamine and aromatic dianhydrides through high temperature solution imidization technique. The polyimides were fully characterized by viscosity measurements, solubility test, FT-IR and 1 H-NMR spectroscopy, X-ray diffraction, differential scanning calorimetry, and thermogravimetry. The X-ray diffraction patterns indicated that all these polyimides were amorphous. The polyimides exhibited good solubility in organic solvents. The glass transition temperature values were observed in the temperature range 210-287°C. Thermogravimetric analysis indicated that 10% weight loss occurred in the temperature range 385-463°C.