| abstract |
An improved synthesis for PMR-type polyimides, including first preparing a dimer of 5-norbornene-2,3-dicarboxylic acid, or acid ester or anhydride and 4,4'methylene dianiline. This dimer is then reacted with one of the following: n 1. the reaction product of a primary aromatic diamine and an aromatic dianhydride. n 2. an aromatic dianhydride. n 3. a mixture of a primary aromatic diamine and an aromatic dianhydride, or an ester of an aromatic tetraacid or an aromatic tetraacid. n The resulting polyimide prepolymer exhibits superior physical properties and is substantially free of undesired impurities and unreacted 4,4'-methylene dianiline. |