| Abstract: | Verdazyl, a new type of stable free radical, was found to inhibit effectively the radical polymerization of styrene and methyl methacrylate. Inhibition period measured by dilatomethry was proportional to the concentration of verdazyl. The reaction prodacts formed in the system such as N-benyl-verdazyl, N-2-(2-carbomethoxy)propyl-verdazyl and the deduced reaction product, leucoverdazyl, had no effect on the measurement of inhibition period. 2-(2-Cyano)propyl-verdazyl dissociates at temperatures over 40°C but does not interfere the determination of inhibition period at 30°C. The rate of initiation reaction and the ratio of rate constants, k2p/2kt, which were calculated from the consumption rate ofDPPH and from the relationship between polymerization rate and the degree of polymerization. The absorption of verdazyl, at 720 mμ enables to measure inhibition periods from the change of the intensity of the absorption. Polymerizations of vinyl chloride and acrylontrile were also inhibited by verdazyl. Determination of the inhibition period for vinyl acetate was difficult, because the time-conversion curves after the inhibition period were not linear. Polymeric verdazyl also inhibits the radical polymerization of Vinyl monomers. |
