Kinetics of radical polymerization—XXXVII. Investigation of molecular-inhibitors in the radical polymerization of acrylonitrile

The effect of molecular inhibitors with different reactivities was studied for the homogeneous (solution) and heterogeneous bulk-polymerization of AN. p-Nitro-acetophenone, which acts as a weak retarder in solution, strongly decreases the accelerating character of the bulk polymerization. Aromatic nitroso-compounds are strong inhibitors in both homogeneous and heterogeneous polymerizations. The length of the inhibition period depends linearly on the inhibitor concentration. The character and kinetics of the polymerization after the inhibition period are not affected by the nitroso compounds. A novel method has been introduced to determine the length of inhibition period for accelerating heterogeneous polymerization. In every studied system, a considerable stoichiometric anomaly was observed, and attributed to the hot radical effect.