Synthesis and Properties of Polyimides from Aromatic Dianhydrides Having Various Number of Phenylene Units and B is {4-[4-(4-aminophenoxy)phenoxy]phenyl} Ether

A new para-substituted aromatic ether diamine, bis{4-[4-(4-aminophenoxy)phenoxy]phenyl} ether 1, was synthesized in four steps starting from 4,4'-dibromodiphenyl ether. New aromatic polyimides, with 5 ether linkages per monomer unit, were prepared from this diamine and various tetracarboxylic dianhydrides, pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (DA-0), 3,3 '',4,4 ''-p-terphenyltetracarboxylic dianhydride (DA-1), 3,3 ''',4,4 '''-p-quarterphenyltetracarboxylic dianhydride (DA-2), 3,3 '''',4,4 ''''-p-quinquephenyltetracarboxylic dianhydride (DA-3), and 3,3 ''''',4,4 '''''-p-sexiphenyltetracarboxylic dianhydride (DA-4), by a conventional two-step procedure that included ring-opening polymerization in N-methylpyrrolidone (NMP) and subsequent thermal cyclic dehydration. The polyimides were characterized by wide-angle X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry (TG), and dynamic mechanical analysis (DMA). PI-PMDA from PMDA and PI-m (m = 0-4) from DA (m = 0-4) had glass transition temperatures (T-g) at 290 degrees C and 200-210 degrees C, respectively. The thermal properties, adhesion properties heated at 400 degrees C, dielectric constants (epsilon) and water absorption of the polyimides were compared and discussed on the basis of the number (m) of phenylene units in the dianhydrides.