Several ortho-disubstituted benzonorbornadiene derivatives are described. These molecules contain acid, ester, or anhydride functionality permitting their use as end caps in PMR (polymerization of monomer reactants) polyimide systems. The replacement of the currently used norbomenyl end caps with benzonorbornadienyl end caps affords resins of increased aromatic content. It also allows evaluation of some mechanistic aspects of PMR cross-linking. Initial testing of AAphenylimide model compounds and of actual resin formulations using the benzonorbornadienyl end cap reveals that they undergo efficient thermal crosslinking to give oligomers with physical properties and thermal stability comparable to commercial norbomeneend-capped PMR systems. (polymerization of monomer reactants), developed jointly by NASA and TRW,1 is a commercially important polyimide-based composite with good high-temperature properties. Imidization of the indicated monomers (eq 1) is followed by a higher temperature curing.

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