Synthesis and characterization of some Schiff-base-containing polyimides

The diamine, 4-aminophenyloxy-N-4-[(4-amiophenyloxy)benzylidene]aniline, was prepared via the nucleophilic substitution reaction and was polymerized with different dianhydrides either by one-step solution polymerization reaction or two-step procedure. The latter includes ring-opening polyaddition to give poly(amic acid), followed by cyclodehydration to polyimides. The inherent viscosity ranges from 0.61-0.79 dl/g. Some of the polymers were soluble in most of the organic solvents such as DMSO, DMF, DMAc, NMP, and m-cresol even at room temperature. The degradation temperature of the resultant polymers falls in the ranges from 240-500 degrees C in nitrogen with only 10% weight loss. Specific heat capacity at 200 degrees C ranges from 1.0929-2.6275 J g(-1) k(-1). The temperature at which the maximum degradation of the polymer occurs ranges from 600-630 degrees C. The glass transition temperature (Tg) values of the polyimides ranged from 185 to 272 degrees C. The activation energy and enthalpy of the polyimides ranged from 47.5-55.0 kJ/mole and 45.7-53.0 kJ/mole and the moisture absorption in the range of 0.23-0.72%.