Charge-transfer complexes as polymerisation inhibitors: III. Studies on the mechanism of inhibition and retardation of styrene polymerisation by N,N-dimethylaniline-chloranil complexes

The mechanism of inhibition and retardation of the sensitised polymerisation of styrene has been investigated using the charge-transfer complexes of N, N-dimethylaniline (DMA) with chloranil. The results support the idea that the inhibition reactions involve electron-transfer from the growing chains to the quinone to form polymeric cations and semiquinone anions. The latter are the actual inhibiting species and the inhibiting efficiency is determined by the extent to which they are found as kinetically independent species in the polymerising system. The inhibition reactions should accordingly be considered as oxidation-reduction processes in which the growing chains are the electron-donors.