HYDROLYSIS OF SODIUM-2-ACRYLAMIDO-2-METHYLPROPANESULFONATE COPOLYMERSAT ELEVATED-TEMPERATURE IN AQUEOUS-SOLUTION VIA C-13 NMR-SPECTROSCOPY

The stability of sodium-2-acrylamido-2-methylpropanesulfonate (P), cop olymerized with acrylamide (M) or acrylic acid (A), towards amide hydr olysis at > 100-degrees-C is examined. Two copolymers, with average st ructural sequences of MMMP (polymer I) and APAP (polymer II), were age d at high temperature in 0.1 N NaCl and the hydrolysis monitored by in tegration of carbonyl resonances. M hydrolysis in polymer I at pH 8 (e nergy of activation = 85.9 kJ mol-1) is 10 times greater at 150-degree s-C than at 120-degrees-C and is unaffected by the presence of P. P hy drolysis occurs in two steps for both polymers at 150-degrees-C. The i nitial hydrolysis rate increases dramatically after half of the P unit s are hydrolysed. Intramolecular P hydrolysis catalysed by an adjacent dissociated carboxylate in A is proposed to explain the rapid hydroly sis. 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 polyme r. At pH 8 and 150-degrees-C, P in polymer II is two times more stable than in polymer I lasting 9 days before complete hydrolysis occurs.