Isotactic (type II)polymers of methyl methacrylate are obtained from anionic polymerizations initiated by organolithium compounds at low temperature ( −70°)in toluene solution. The presence of small amounts of various ethers leads to polymers of reduced isotacticity; the effectiveness of these ethers in disrupting stereospecificity can be related semiquantitatively to their Lewis base strength. Certain Grignard reagents also produce highly isotactic polymer of methyl methacrylate, while others lead to less stereospecific results. The nature of the inorganic component of such initiators appears to determine the steric course of the addition reaction. The formation of a magnesium halide–monomer complex may be involved.

The polymerization of methyl methacrylate and isopropyl acrylate in toluene with phenyl‐H3‐magnesium bromide has been studied at 0 and −70°C., respectively. Comparison of number‐average molecular weights calculated from measurement of radioactivity and from measurements of appropriate colligative properties has shown that there is one and only one phenyl group per chain. Thus, initiation in this system is by 1,4‐addition of the organomagnesium compound to the monomer. Methyl methacrylate, isopropyl acrylate, ethyl acrylate, and methyl acrylate were polymerized in toluene with phenylmagnesium bromide as the initiator. Isolation and identification of all the products have shown that, in addition to polymer, there are formed small amounts of two ketones and a hydrocarbon. Data are presented indicating that the principal mode of termination is via an intramolecular cyclization to give chains having a β‐ketoester group on the end (arising from intramolecular reaction). A rationale for the stereospecificity, the termination reaction, and the large ratios of weight‐average to number‐average molecular weight in these polymerizations is proposed.

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ethyl acetate. Removal of the ethyl acetate under vacuum and distillation of the residual brown oil gave 52% of material boiling at 121-127°/0.1 mm., re" 1.4755.

SynopsisThe aqueous suspension chlorination of poly( methyl methacrylate) using incandrsrrnt light produces polymer having up to one chlorine atom per monomer unit. The mrchmism of aqueous suspension chlorination is the same as that for solution chlorination, i.r., free radical substitution; the rate of chlorination a t constant chlorine flow rate drprnds on the time, the concentration of the polymer, and the size or porosity of the polymer particles. The structures of suspension and solution Chlorinated poly( methyl methacrylate) were established by comparison of their NMR spectra with those of poly(methy1 methacrylate), poly(chloromethy1 methacrylate), and a copolymer of methyl a-chloromethylacrylate with methyl methacrylate. In chlorinated poly( methyl methacrylate) having 0.5 chlorine atoms per monomer unit, hrtlf of the chlorine is on the ester methyl group and half is on the @-carbon atom. In the suspension chlorinated sample containing one chlorine per monomer unit, 20% of the chlorine is present as OCHC1, groups, 40% as OCHtC1 groups, 30% as -CHCl-groups, and lOyo as C-CH&1 groups. In a solution chlorinated sample containing two chlorine atoms per monomer unit, the chlorine is distributed: 40% as OCH,Cl, 40% as -CHCl-and/or C-CH,CI, and 20% as OCHCl?.