Thermosetting acetylene‐terminated polyphenylquinoxalines

A series of acetylene‐terminated phenylquinoxaline oligomers have been prepared which cure by addition, without the evolution of volatiles. The synthesis utilized the novel terminal acetylene end‐capping reagent, 3‐(3,4‐diaminophenoxy)phenylacetylene. The end‐capped oligomers were soluble (20–30%) in low‐boiling organic solvents and exhibited a high degree of flow at their softening temperatures. Thermal analytical data obtained on the oligomers indicated initial softening in the vicinity of 160°C and a strong polymerization exotherm reaching a maximum at 274°C. Cured samples (8 hr at 280°C) exhibited Tg values of approximately 320°C. Mass spectrometry–thermogravimetric analysis of the polymers demonstrated that no volatiles were emitted during cure, and that decomposition of the resins initiated at 465°C. Synthetic routes to the acetylene terminated phenylquinoxaline oligomers and the end‐capping reagent are discussed as well as the physical properties of the oligomer and cured system.