STABILITY AND DEGRADATION OF POLY(1,4-PHENYLENE-1,3,4-OXADIAZOLE) MOLECULES IN SULFURIC-ACID

The translational diffusion coefficient and intrinsic viscosity of pol y(1,4-phenylene-1,3,4-oxadiazole) molecules in 96% H2SO4 have been det ermined at different stages of degradation of the molecules in acid so lution at temperature ranging from 82 to 105 degrees C. The degradatio n rate constant, k, has been obtained from the change in the molecular weight, M, of the product degraded in solution with time at high temp erature. The activation energy of the hydrolysis process was 103 +/- 7 kJ mol(-1), which is smaller than that of aromatic polyamides in the same solvent. According to our hydrodynamic data, the degree of coilin g of the molecules of degraded products does not differ from that of u ndegraded samples, and our conclusion was that the degradation is not accompanied with a noticeable change in the short-range interactions i n the molecular chain and may be understood as a random chain scission . (C) 1998 Elsevier Science Limited. All rights reserved.