The stereoregular polymerization of methyl methacrylate by Grignard reagents as affected by various alkyl groups, polymerization temperatures, and organic additives has been studied. These three factors were found to be effective in controlling the stereoregularity of PMMA. It has been confirmed that bands sensitive to stereoregularity at 757 and 749 cm.−1 correspond to isotactic and syndiotactic segments, respectively. Isotaxy and syndiotaxy were determined by the infrared method. Proton magnetic resonance spectra were found to be useful in analyzing the stereoregularity of PMMA and in estimating the amounts of stereoregular components in the polymer chains. Three elementary stereoregular units were proposed: isotactic, syndiotactic, and disyndiotactic. The kinetics of the polymerization reactions were studied in the cases of n‐butyl and isobutyl magnesium bromide. The rates of polymerization were found to be proportional to monomer concentration and to the square of the initiator concentration and molecular weight was proportional to monomer concentration and inversely proportional to initiator concentration. The rate of polymerization is maximum at a certain temperature. Branched‐alkyl Grignard reagents were found to produce isotactic polymer. Straight‐chain, alkyl‐type Grignard reagents, with the exceptions of n‐octyl‐ and n‐hexylmagnesium bromide, produce usually stereoblock polymer. Phenylmagnesium bromide (above 0°C.) and cyclohexylmagnesium bromide produce isotactic polymer. Low‐temperature, free‐radical polymerization results in almost wholly syndiotactic polymer. Ordinary free‐radical polymer has a stereoblock strucutre composed of syndiotactic and disynodiotactic units with smaller amounts of isotactic material. The addition of dioxane, pyridine, diphenylamine, or diethylamine promotes polymerization. Use of the latter two amines results in isotactic polymer.

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