STABILITY AND DEGRADATION OF POLY(NAPHTHO YLENEIMIDOBENZIMIDAZOLE)

The change in strength characteristics of poly(naphthoyleneimidobenzim idazole) films and fibers during aging in air at room temperature was shown to be accompanied by the slow degradation of the macromolecules. The degradation was proven by the fact that in concentrated sulfuric acid the polymer exhibited lower intrinsic viscosity, a greater transl ational diffusion coefficient, and a smaller characteristic orientatio n in flow birefrigence experiments. The decrease in molecular mass was greatly accelerated when poly(naphthoyleneimidobenzimidazole) was in the powder state. Resynthesis (heating in vacuum at 200-degrees-C) res ulted in partial recovery of the molecular mass; however, both resynth esized and reprecipitated (into the water) samples retained the trend toward self-degradation.