THERMAL-ISOMERIZATION STUDIES OF THE 2 LOWEST MOLECULAR-WEIGHT COMPONENTS OF A NADIMIDE END-CAPPED THERMOSET

The mechanism of endo-exo isomerization of nadimide groups was investi gated on 4,4'-methylene dianiline bis-5-norbornene-2, 3-dicarboximide (named PDO) which involves three configuration isomers and on a nadimi de end-capped oligomer (D1) both corresponding to the lowest molecular weight species of an oligobenzhydrol-imide nadimide end-capped thermo set (IP960). Isomerization kinetic versus temperature and pressure was studied by H-1 nuclear magnetic resonance. The results indicate that isomerization leads to a thermodynamic mixture composed of almost equa l amounts of endo and exo configurations. It was also observed that th ermal isomerization of PDO was possible below its melting point and th at thermal isomerization under reduced pressure produced maleimide der ivatives.