The stability of sodium-2-acrylamido-2-methylpropanesulfonate (P), copolymerized with acrylamide (M) or acrylic acid (A), towards amide hydrolysis at > 100°C is examined. Two copolymers, with average structural sequences of MMMP (polymer I) and APAP (polymer II), were aged at high temperature in 0.1 N NaC1 and the hydrolysis monitored by integration of carbonyl resonances. M hydrolysis in polymer I at pH 8 (energy of activation= 85.9 kJ mo1-1) is 10 times greater at 150°C than at 120°C and is unaffected by the presence of P. P hydrolysis occurs in two steps for both polymers at 150°C. The initial hydrolysis rate increases dramatically after half of the P units are hydrolysed. Intramolecular P hydrolysis catalysed by an adjacent dissociated carboxylate in A is proposed to explain the rapid hydrolysis. Nearby Ps prohibit this hydrolysis. The initial P hydrolysis rate in polymer II is enhanced five times on decreasing the pH from 8 to 6 due to decreased Coulombic repulsion between hydroxide and the polymer. At pH 8 and 150°C, P in polymer II is two times more stable than in polymer I lasting 9 days before complete hydrolysis occurs.
Посилання на статтю:
Hydrolysis of sodium-2-acrylamido-2- methylpropanesulfonate copolymers at elevated temperature in aqueous solution via 13C n.m.r, spectroscopy / W. O. Parker Jr and A. kezzi // Polymer. – 1993. – Vol 34. – P. 4913-4918.