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Polyimide oligomers (prepolymers) and resins of the PMR-15 type have been prepared from 5-norbomene-2,3-dicarboxylic half acid ester (NE), 3,3',4,4'-benzophenone tetracarboxylic diester (BTDE) and a series of diamines incorporating 1,2,3-triazole, quinoxaline, pyrido[2,3-b]pyrazine, pyrido[3,4-b]pyrazine, benzo[g]quinoxaline, pyrazino-[2,3]-d]pyridazine and bis(pyrido[3,4-b]pyrazino)benzene ring systems. Two tetraamines in the bis(pyrazino[2,3-d]pyridazino)benzene ring system were also employed. Selected diamine monomers from the above ring systems provde PMR-15-analogue resins of higher thermal and thermooxidative stability than PMR-15 itself. The physical behaviour during oligomerization and curing of PMR systems has been studied by dynamic mechanical thermal analysis (DMTA). Traces akin to that from PMR-15 are obtained using certain diamine monomers (e.g. triazole and pyrido[3,4-b]pyrazine containing) but a featureless thermogram is observed using tetraamines in the bis(pyrazino[2,3-dj]pyridazino) benzene system.

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