| abstract |
A polybenzimidazole having a polymer chain with the following repeating unit: <IMAGE> R2 is a divalent carbon ring with the linkage to an adjacent repeating unit through adjacent carbon atoms of the ring. Such polybenzimidazoles are formed by the condensation of (a) a substitute carbon ring compound, having at least one dicarboxylic anhydride or its equivalent substituted at adjacent carbon atoms and (b) an organic tetraamine of the following formula: <IMAGE> Polybenzimidazoles of the foregoing type may be formed by the use of a tetracarboxylic dianhydride in the condensation reaction. These cross-linked polymers are characterized by minimal softening or burning at high temperature. |