Ozone treatment of water‐soluble polymers. III. Ozone degradation of polyacrylamide in water

Polyacrylamide (MW 350,000) was ozonized at pH 2 and pH 10 buffer solution. There was little ozonization at pH 2, but at pH 10 the COD and the viscosity of the solution decreased upon ozonization, and a linear relationship existed between the ozone consumed and the number of breaks calculated from the viscosity. This relationship apparently indicated that 45 molecules ozone were consumed for one cleavage of the polymer chain. Such random cleavage was confirmed also by the observation of molecular weight distribution by means of gel filtration chromatography. The amide group decreased scarcely by the ozonization, while a small amount of aldehyde was observed in the ozonized solution. No remarkable change was observed in the IR spectra of the ozonized sample, except for a weak absorption band at 1725 cm−1 which arose from the carbonyl of aldehyde or ketone. Although no variation was observed in the 13C NMR spectra either, a strong absorption peak at 266 nm appeared in the UV spectra of the ozonized solution and increased with the ozonization time. This phenomenon was presumed to be due to the formation of a certain ring structure between the amide group and the small amount of ketone produced in the main chain. However, the details of the ozonization mechanism could not be ascertained.