Abstract
Enantiomer-selective polymerization of (RS)-α-methylbenzyl methacrylate [(RS)-MBMA] was investigated in toluene at −30°C. Reaction products between cyclohexylmagnesium bromide (cHexMgBr) and axially dissymmetric 2,2′-diamino-6,6′-dimethylbiphenyl (AMB) in the mole ratio of 1.5:1 were used as a chiral initiating system. The polymer produced contained a biphenyl group from the catalyst fragment. The polymerization proceeded in an anionic coordination mechanism and the racemic monomer was kinetically resolved during the course of the reaction. The enantiomer selectivity ratio when using (R)-AMB was estimated to be r(S)=18.0 according to the integrated composition equation for an “ideal” copolymerization of the enantiomeric monomers. Most parts of the polymer were found to be of full isotacticity from inspection of the 13C NMR spectrum. Some physical properties of the polymer strongly suggested that it is a mixture of (R)- and (S)-homopolymers. This may be an example of an asymmetric-selective (stereoelective) and stereoselective polymerization of vinyl monomer. In the copolymerizations between (RS)-MBMA and achiral methacrylates, the catalyst also showed high selectivity toward (RS)-MBMA. Each of the copolymers from methacrylates of methyl, benzyl, and diphenylmethyl alcohols was coisotactic, and the enantiomer selections were consistent with that observed for the homopolymerization. On the other hand, both the isotacticity of copolymer and the selection greatly decreased in the copolymerization with α,α-dimethylbenzyl methacrylate which has no hydrogen at the α-carbon of the ester group.
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Kanoh, S., Goka, S., Murose, N. et al. Highly Asymmetric-selective and Stereoselective Polymerization of (RS)-α-Methylbenzyl Methacrylate with Cyclohexyl-magnesium Bromide-Axially Dissymmetric 2,2′-Diamino-6,6′-dimethylbiphenyl System. Polym J 19, 1047–1065 (1987). https://doi.org/10.1295/polymj.19.1047
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DOI: https://doi.org/10.1295/polymj.19.1047
