Synthesis and Properties of Novel p-Aramid Including Pyrazine Ring

Poly[p-phenylene(2,5-di-p-carbonylphenylpyrazine)amide] (PPPA) was synthesized by the polycondensation of 2,5-di-p-chloroformylphenylpyrazine with p-phenylenediamine. Dicarboxylic acid was prepared by dimerization of p-cyanophenacyl bromide. Molecular characterization was carried out by IR and NMR. PPPA is soluble in sulfuric acid, forming liquid crystals. The temperature at the 10 wt% loss in TGA was 545°C. The fiber spinning was difficult due to the strong tendency to crystallization and rapid relaxation from liquid crystalline state. From the X-ray diffraction pattern of uniplanar oriented film of PPPA, approximate lattice constant was evaluated as a=7.94 A, b=5.23 A, and c=20.6 A (fiber axis). Fiber period agreed with the identity period for all trans conformation of PPPA. Tensile modulus along the molecular axis was estimated as 210–220 GPa by referring to the theoretical moduli of poly(p-phenyleneterephthalamide) and poly(p-phenylene).