a tough , high performance polyimide is provided by reacting a triple bond conjugated with an aromatic ring in a bisethynyl compound with the active double bond in a compound containing a double bond activated toward the formation of a diels - adler type adduct , especially a bismaleimide , a biscitraconimide , or a benzoquinone , or mixtures thereof . addition curing of this product produces a highly linear polymeric structure and heat treating the highly linear polymeric structure produces a thermally - stable aromatic addition - type thermoplastic polyimide , which finds utility in the preparation of molding compounds , adhesive compositions , and polymer matrix composites .