A. Giz et al., Kinetics and mechanisms of acrylamide polymerization from absolute, onlinemonitoring of polymerization reaction, MACROMOLEC, 34(5), 2001, pp. 1180-1191
An automatic, continuous, online monitoring technique was used to follow th
e polymerization of acrylamide under a variety of temperature and initiator
conditions, without chromatographic columns. The technique furnishes, as a
function of time, the weight-average polyacrylamide mass M-w, the monomer
conversion, reduced viscosity, and certain measures of polydispersity. Afte
r a complex initial phase following initiator addition, wherein impurities
competed with monomer for free radicals, monomer conversion followed a firs
t-order decay during most of the subsequent reaction. For fixed monomer con
centration, at every point in conversion beyond very early points, M-w was
proportional to the inverse square root of the initiator concentration. Fur
thermore, the monomer decay time also scales in the same way, and M-w vs co
nversion is linear during most of the conversion, with a negative slope. He
nce, the overall reaction scheme falls within the quasi-steady state approx
imation (QSSA) of ideal polymerization kinetics. The rate constant for init
iator decay, as well as the ratio of propagation rate constant squared to t
ermination rate constant were determined. The activation energy for the pot
assium persulfate initiator decomposition was also determined. Deviations f
rom the ideal kinetics at early and late conversion are rationalized by exi
sting models. Using a technique for determining instantaneous polydispersit
y from the derivative of M-w, it was possible to follow the evolution of th
e polydispersity for the polyacrylamide reactions.