Hydrolysis of cationic polyacrylamides

The alkaline hydrolysis of two acrylamide-based polyelectrolytes has been investigated. The experiments were carried out in buffered aqueous solutions in the pH range of 3.5–8.5 and in the temperature range of 22–50°C. ¹³C-NMR analysis of the hydrolysis product showed that choline chloride was the substance released upon hydrolysis. The decrease in charge density of the copolymer due to the hydrolysis was studied by polyelectrolyte titration and nitrogen analysis. The results show that the rate of hydrolysis increased with increasing pH or increasing temperature. In the hydrolysis of C-PAM 1 at 22°C and pH 6, the half-life of the cationic groups was 10 days. At pH 7 the half-life was shorter, 24 h, and at pH 8.5 the reaction was very fast with a half-life of about 0.25 h. The charged groups on C-PAM 2, the polymer with the higher charge density of the two polymers studied, have somewhat longer half lives than those on C-PAM 1. This can be explained by the structure of the polymers.