Characterizations and thermal stability of soluble polyimide derived from novel unsymmetrical diamine monomers

Two kinds of novel aromatic, unsymmetrical diamines with ether ketone group, 3-amino-4'-(4-amino-2-trifluoromethylphenoxy)-benzophenone and 3-amino-4'-(4-aminophenoxy)-benzophenone, was successfully synthesized by two different synthetical routes and polymerized with various aromatic tetracarboxylic acid dianhydrides, including 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 2,2'-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride, via a conventional two-step thermal or chemical imidization method to produce a series of fluorinated polyimides. The polyimides were characterized with solubility tests, viscosity measurements, mechanical properties tests, IR-FT, and thermogravimetric analysis. The polyimides had inherent viscosities of 0.54-0.77 dL/g and were easily dissolved in both polar, aprotic solvents and common, low-boiling-point solvents. The resulting strong and flexible polyimide films exhibited excellent thermal stability, with decomposition temperatures (at 10% weight loss) above 573 degrees C and glass-transition temperatures in the range of 222-251 degrees C. Moreover, the polymer films showed outstanding mechanical properties, with tensile strengths of 86.5-121.6 MPa, elongations at break of 9-16%, and initial moduli of 1.26-1.97 GPa. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced applications. (C) 2010 Elsevier Ltd. All rights reserved.