Kinetics of radical polymerization of N ‐vinylpyrrolidone by peroxidiphosphate–Ag + system

The kinetics of aqueous polymerization of N ‐vinylpyrrolidone ( N ‐VP) was carried out using potassium peroxidiphosphate–Ag + system under nitrogen atmosphere at 25°C. The rate of polymerization was directly proportional to the concentration of the N ‐vinylpyrrolidone and showed a half‐order with respect to the concentration of the peroxidiphosphate (H 2 P 2 O   8 2− ) and Ag + ions. The value of κ p /(κ t ) 1/2 was computed and its value found to increase on increasing the temperature of the reaction mixture. The energy of activation ( E a ) was found to be 65.8 ± 0.1 kJ mol −1 within the temperature range from 20 to 50°C. Viscometric average molecular weight of polyvinylpyrrolidone was determined by measuring intrinsic viscosity of the polymer samples collected at different kinetic conditions. The effect of various additives was also studied. A suitable mechanism of polymerization has been proposed and a reaction rate law was derived considering experimental results. © 1994 John Wiley & Sons, Inc.