PULSED-LASER STUDY OF THE PROPAGATION KINETICS OF ACRYLAMIDE AND ITS DERIVATIVES IN WATER

The pulsed laser polymerization method has been-applied to aqueous acr ylamide (AAm) in the absence and presence of 3 mol dm-3 propionamide t o obtain the propagation rate coefficient (k(p)) as a function of temp erature. Below ca. 50-degrees-C in the absence of propionamide, k(p) d ecreases with increasing temperature. It is proposed that this is due to the existence of an H-bonded intermediate complex along the reactio n coordinate, which at low temperatures enhances propagation but which breaks down at higher temperatures. In the presence of propionamide o r above 50-degrees-C in the absence of propionamide, the temperature d ependence of k(p) behaves normally, supporting the proposition. Assumi ng that the high-temperature rate represents ''normal'' propagation in the absence of the formation of complex, k(p) = 7 x 10(6) dm3 mol-1 s -1 exp[-(21 +/- 2 kJ mol-1)/RT]. Analysis of these results suggests th at the driving force behind the proposed intermediate complex could be H-bonding in nature. Studies of k(p) for alpha-methyl- and N-methyl-s ubstituted AAm derivatives indicate that the former imposes greater co nstraints upon the propagation pathway than the latter.