Abstract
Three new hydrazo-bridged diamines, 4,4'-bis [4-(4-aminophenyloxy) phenylhydrazy]] biphenyl (BPD-2), 4,4'-bis [4-(4-aminophenyloxy) phenylhydrazy]] biphenyl ether (SPD-2) and 4,4-bis [4-(4-aminophenyloxy) phenyl] hydrazine (APD-2), were synthesized by the reduction of three azo-diols, 4,4'-bis (4-azo-1-hydroxyphenyl) biphenyl (BPD), 4,4'-bis (4-azo-1-hydroxyphenyl) biphenyl ether (SPD) and azo-4-hydroxybenzene (APD), and polymerized with pyromellitic dianhydride (PM), 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BP) and 3,4,9,10-perylenetetracarboxylic acid dianhydride (PR) either by one-step solution polymerization or by two-step procedure which includes ring-opening polyaddition to give poly(amic acid) followed by cyclic dehydration to polyimide. The monomers and polyimides were characterized by their elemental analyses, FTIR and H-1 NMR spectroscopy. Glass transition temperatures of the polymers are quite high (175-310 degrees C), characteristic of polyimides. The decomposition temperatures for 10% weight loss fall in the range of 280-575 degrees C in nitrogen. Activation energies of pyrolysis for each of the polymers calculated from Horowitz and Metzger's method are also high (52.54-95.28 kJ mol(-1)). The inherent viscosities of the polyimides at a concentration of 0.5 g/dl in DMF range from 0.94 to 1.93 dl/g. (C) 2008 Elsevier Ltd. All rights reserved.