Abstract
Polyacrylamide was quantitatively hydroxymethylated with formaldehyde in an alkaline solution in the presence of catalytic triethylamine. This reaction in an acidic medium is proved unsatisfactory due to gel formation. The pH of the medium affected the reaction between N-methylol polyacrylamide and dimethylamine, slightly alkaline conditions being favorable. Thus, when the hydroxymethylated polymers were treated with dimethylamine in a molar ratio of 1:3 at pH 12, 70°C, for 0.5 hr, approximately 75% of the total methylol groups. were aminomethylated. In a more alkaline solution, the polymers tend to undergo hydrolysis to form carboxyl groups along the molecular chain. In an acidic solotion, on the other hand, gelation is unavoidable. N-Dimethylaminomethyl polyacrylamide is conveniently perpared by treating polyacrylamide with formaldehyde followed by dimethylamine withoutisolating the N-methylol intermediate. However, simultaneous treatment of polyacrylamide with both of the reactants is not recommendable because of the difficulty in controlling the reaction. N-Methylol and N-dimethylaminomethyl polyacrylamides are soluble in water and formamide, and insoluble in other organic solvents. The N-dimethylamino methyl polymer serves as a cationic polyelectrolyte.
