New polymerization catalysts for methyl methacrylate

New free radical catalysts for the polymerization of methyl methacrylate and other acrylic monomers have been reported. They comprise mixtures or salts of N,N‐dialkyl aryl amines and o‐benzoic sulfimide (saccharin). A p‐substituent on N,N‐dimethylaniline or N,N‐diethylaniline had a significant influence upon polymerization. Electron‐donating groups such as methyl or methoxy increased the total yield of the polymer, while electron‐withdrawing groups, namely, chlorine, bromine, or aldehyde, reduced the yield of the polymer. When electron‐withdrawing groups, namely, nitro, nitroso, or phenylazo, were present in the para position of dimethylaniline, no polymer was obtained. Presence of a methyl group in the meta position in dimethylaniline enhanced the yield of the polymer. However, when a methyl group was present in the ortho position, the yield of the polymer was significantly reduced, probably due to a steric factor. Binary mixtures containing equimolar proportions of saccharin and the amine were better initiators for methyl methacrylate polymerization than the corresponding salts of saccharin and amine. A number of organic acids in admixture with dimethylaniline also polymerized methyl methacrylate. The stronger the acid, the greater was the yield of the polymer. However, the yields were considerably lower than in case of dimethaniline‐saccharin mixture as catalyst.