Heteroaromatic polymers -: High temperature polypyrrolones derived from 2,6-bis(3′,4′-diaminophenyl)-4-biphenylpyridine and various aromatic dianhydrides

A new type of aromatic tetraamine containing biphenyl moiety in the side chain was synthesized via a modified Chichibabin's reaction. 3-Nitro-4-acetamidoacetophenone was reacted with 4-phenyl benzaldehyde in the presence of ammonium acetate to obtain 2,6-bis(3',4'-diaminophenyl)-4-biphenyl pyridine (DPPA). A series of polypyrrolones (PPys) were prepared using tetraamine and various aromatic dianhydrides via a two-step cyclization procedure. All the PPys show excellent high temperature stabilities with the initial decomposition temperatures of 530-549 degrees C and residual weight ratio of 49%-80% at 750 degrees C in nitrogen. The polymers exhibit no apparent glass transition temperatures (T(g)s) except PPy-1 (T-g = 327 degrees C), which is derived from tetraamine DPPA and 2,2-bis[4-(3',4'-dicarboxyphenoxy)-phenyl] propane dianhydride (BPADA). In addition, the polymers have acceptable mechanical properties with the tensile strength of 65-94 MPa. The PPy films show excellent hydrolysis-resistance in alkaline aqueous medium and could maintain most of the properties even after boiling in 10% aqueous sodium hydroxide solution for a week.