WAXD EVIDENCE FOR A THERMALLY-INDUCED ISOMERIZATION IN THE CRYSTALLINE STATE OF A NADIMIDE END-CAPPED THERMOSET MODEL-COMPOUND

The kinetically controlled thermal isomerization of the nadimide endo to exo configuration was investigated in the solid state. Experiments were conducted on 4,4'-methylene dianiline bis-5-norbornene-2,3-dicarb oximide, which is the lowest molar mass compound common to two nadimid e end-capped thermosets (the well-known commercially available PMR-15 and a soluble oligobenzhydrolimide). WAXS diffractograms of isomerized moieties, recorded at increasing temperatures, lead to the conclusion that the isomerization can occur in the crystalline state, through re tro-Diels-Alder and Diels-Alder reactions.