Abstract

The free radical polymerization of vinyl monomers is efficiently inhibited by ?-nitrostyrene derivatives. The high reactivity of the growing radicals towards the ?-nitro compounds is controlled by the electron-donor character of the double bond of the ?-nitro derivative. Electron withdrawing substituents at the 4-position of ?nitrostyrene increase markedly the inhibition rate. The inhibition efficiency of ?-nitrostyrenes towards electron deficient monomer double bonds is strongly reduced. Polymerization rates and 1H NMR results show that the ?nitrostyrene derivatives act as a mechanism that involves the release of NO2.