Peter N. Lavrenko, Olga V. Okatova, Burkhard Schulz

• The translational diffusion coefficient and intrinsic viscosity of poly(1,4-phenylene-1,3,4-oxadiazole) molecules in 96% H2S04 have been determined at different stages of degradation of the molecules in acid solution at temperature ranging from 82 to 105 °C. The degradation rate constant, k, has been obtained from the change in the molecular weight, M, of the product degraded in solution with time at high temperature. The activation energy of the hydrolysis process was 103 ± 7 kJmol-1, which is smaller than that of aromatic polyamides in the same solvent. According to our hydrodynamic data, the degree of coiling of the molecules of degraded products does not differ from that of undegraded samples, and our conclusion was that the degradation is not accompanied with a noticeable change in the short- range interactions in the molecular chain and may be understood as a random chain scission.