Dianhydrides used as precursors to these materials include pyromellitic dianhydride, benzoquinonetetracarboxylic dianhydride and naphthalene tetracarboxylic dianhydride. Common diamine building blocks include 4,4'-diaminodiphenyl ether ("DAPE"), meta-phenylenediamine ("MDA"), and 3,3-diaminodiphenylmethane.[1] Hundreds of diamines and dianhydrides have been examined to tune the physical and especially the processing properties of these materials.