Polymerization kinetics of acrylonitrile

It has been found that the polymerization of acrylonitrile dissolved in water proceeds easily in the presence of hydrogen peroxide and iron(III) salts. The kinetic investigation of this reaction shows that it is second order with respect to the monomer. The rate of reaction invreases with the concentration of hydrogen peroxide and of iron(III) salt but it decreases with an increase in the concentration of hydrogen ions. The average molecular weight of the formed polymer was determined by viscosity measurements. The degree of polymerisation increases with the concentration of the monomer and hydrogen ions, but decreases with an increase in the concentration of hydrogen peroxide and iron(III) salt. The reaction is inhibited by dissolved gaseous oxygen. Under otherwise similar conditions, the rate of the decomposition of hydrogen peroxide is considerably decreased in the presence of the acrylonitrile compared with its catalytic decomposition by iron(III) salts without acrylonitrile present. The amount of hydrogen peroxide decompsed on the average is more than two molecules per molecule of the formed polymer. The experimental data are briefly discussed in relation to a plausible reaction mechanism.