The polymerization of methyl methacrylate initiated with ALBN and inhibited with cupric chloride in DMF has been studied at 60°C. Cupric chloride proved to be an " ideal " inhibitor, the post-inhibition rate being equal to the rate obtained in the absence of inhibitor. From a simple inhibition period against cupric chloride concentration plot, the rate constant for the decomposition of AIBN into free radicals was 1.38 x 10-5 sec-1. From a study of the period of acceleration following complete inhibition, a value of 1050 was found for the ratio kx/kp, where kx is the rate constant for the reaction between polymethyi methacrylate radicals and cupric chloride. This leads to a value of 7.7 x 105 1. mole-1 sec-1 for kx at 60°, which is much higher than that for the corresponding reaction with ferric chloride, and is of the order of magnitude of rate constants for radical-radical interaction.

The polymerization of methyl methacrylate initiated with AIBN and inhibited with cupric bromide in DMF has been studied at from 40-70°C. Rate constants for the initiation reaction, obtained by the inhibition period method, were 6.2 x lo-', 3.7 x 1.42 x and 8 x s-l at 40, 50, 60 and 70°C respectively, yielding an activation energy of 137.5 kJ mo1-l. The acceleration period

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