An automatic, continuous, online monitoring technique was used to follow the 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. After a complex initial phase following initiator addition, wherein impurities competed with monomer for free radicals, monomer conversion followed a first-order decay during most of the subsequent reaction. For fixed monomer concentration, at every point in conversion beyond very early points, M w was proportional to the inverse square root of the initiator concentration. Furthermore, the monomer decay time also scales in the same way, and M w vs conversion is linear during most of the conversion, with a negative slope. Hence, the overall reaction scheme falls within the quasi-steady state approximation (QSSA) of ideal polymerization kinetics. The rate constant for initiator decay, as well as the ratio of propagation rate constant squared to termination rate constant were determined. The activation energy for the potassium persulfate initiator decomposition was also determined. Deviations from the ideal kinetics at early and late conversion are rationalized by existing models. Using a technique for determining instantaneous polydispersity from the derivative of M w, it was possible to follow the evolution of the polydispersity for the polyacrylamide reactions.

Exploiting differences in refractivity and ultraviolet absorption between pairs of monomers and their associated polymers, automatic, continuous, online monitoring of polymerization reactions (ACOMP) was extended to copolymerization. ACOMP uses no chromatographic separation columns. Copolymerization of methyl methacrylate and styrene was chosen for developing the method. Both the instantaneous concentrations of comonomers and their incorporation rates into copolymer are obtained, which allows model-independent evolution of the average copolymer composition to be followed. Using the compositional information and simultaneous light-scattering data permits monitoring model-independent M w (cumulative weight-average molecular weight), without requiring measurements in different solvents. Simultaneous use of a viscometer allows a cross check on the light-scattering data. Molecular weight and composition data are used to obtain the copolymer bivariate mass and composition distribution. Monomer reactivity ratios are found by an errors in variables method. The reactivity ratios and composition distribution allow sequence length distributions to be computed.