Aerospace industries have been concerned since long by composite materials using highperformance resins. The PMR-15 resin is now the most commonly used resin for industrial applications at high temperature, i.e., 300 degrees C. Despite its comparative commercial success, the PMR-15 resin and its composites show several disadvantages [toxicity of the aromatic diamine (MDA), poor conservation of monomers solution, laminate microcracking]. The purpose of this work concerns the synthesis, the physico-chemical characterization, and the processing of pure bisnadimide model compound to study the endo/exo isomerization of the endcaps and thermomechanical properties. We show that the isomerization mechanism proceeds by retro Diels-Alder reaction followed by recombination in exo isomer and glass temperature transition is upper than 350 degrees C (380 degrees C).