Degradation of poly(meta-phenyleneoxadiazole) in concentrated sulfuric acid

The stability and degradation of poly[2,5-(1,3-phenylene)-1,3,4-oxadiazole] in 96% sulfuric acid in the temperature range from 75 to 104°C were studied by the methods of translational diffusion and viscometry. It was shown that the thermal treatment of the polymer leads to a monotonic decrease in the reduced viscosity of a polymer solution and causes a reduction in the polymer molecular mass. On the basis of the temperature dependence of the degradation rate constant k, the activation energy of the process was found to be almost equal to that of the para isomer of this polymer (E = 102 ± 8 kJ/mol). However, for poly[2,5-(1,3-phenylene)-1,3,4-oxadiazole], the numerical value of the degradation rate constant in sulfuric acid was ∼2 times higher.