The use of a sensitive electronic paramagentic spectrometer permits one to obtain a number of new quantitative and qualitative data regarding the kinetics of polymerization and behavior of macroradicals with large polymerization depths. In particular, it is shown that in the photopolymerization of methyl methacrylate in a block of considerable number of sequestered macroradicals accumulates in the final stages. On the basis of an investigation of the change of the spectra in the heating of the polymer some assumptions are made concerning the secondary reactions of the radicals and concerning the influence of low-molecular impurities on the velocity of these reactions.

It is well known that during the mechanical degradation of polymers there takes place scission of molecular chains and the formation of macroradicals. It is of considerable interest to study the electron paramagnetic resonance (EPR) spectra of the macroradicals produced by milling, and to compare them with the spectra of the macroradicals formed in the process of polymerization, and also during the irradiation of polymers by gamma rays and neutrons. We may endeavor to compare the amount of macroradicals formed with the extent of mechanical destruction (for instance with the area of the new interface which is formed). In addition, as was found by experience, the macroradicals formed by mechanical scission are good models for the investigation of reactivity since practically all of them are in the newly formed surface layers and are therefore very accessible to various chemical influences. They enter easily into reaction with various agents present in the medium since in this process diffusion from the surface is found in practice not to be a predominating factor. In the present communication we give the first EPR results obtained on mechanically degraded polymers.

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In the article by Dogadkin and Shershnev electron paramagnetic resonance spectra produced in the laboratory of Prof. S. E. Bresler are put forward to confirm the radical mechanism of the interaction of TMTD with raw rubber in the process of vulcanization. After this paper had been printed we learned of the work of B. R. McGarvey and H. M. McConnel, in which analogous spectra were observed in solutions containing bivalent copper ions. As a result it is suggested that the electron paramagnetic resonance spectra of stocks of natural rubber with TMTD are affected by admixtures of copper compounds. The amount of copper calculated from the magnitude of the resonance spectrum amounts to 0.1% by weight in relation to the TMTD. The same spectrum is observed on heating a benzene solution of copper acetate and TMTD. Its intensity increases sharply and irreversibly on heating the solution to 100°. corresponding to 10% of the copper contained in the solution.

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