CHARGE-TRANSFER COMPLEXES AS POLYMERIZATION INHIBITORS - 1. AMINE-CHLORANIL COMPLEXES AS INHIBITORS FOR THE RADICAL POLYMERIZATION OF METHYL METHACRYLATE.

Charge-transfer complexes of N,N-dimethylaniline (DMA) and triethylamine (TEA)with chloranil have been investigated as inhibitors for the sensitized polymerization of methyl methacrylate (MMA) in bulk and in solution. Complete inhibition is achieved by the complexes of both amines followed by retardation only in case of DMA. The higher inhibiting efficiency of the TEA complexes is attributed to their greater stability. The polymers formed in the presence of chloranil alone or its complexes with both amines are quinonoid and contain no combined nitrogen. The results support the idea that inhibition reactions involve electron transfer from the growing chains to the quinone, with formation of molecular complexes of polymeric cations and semiquinone anions. The suggested mechanism affords an explanation for the great differences in the inhibiting power of a particular quinone for the polymerization of different monomers.