Stereospecific Polymerization of Methyl Methacrylate by Organomagnesium Catalysts with a Magnesium-Nitrogen Bond

Abstract

The polymerization of methyl methacrylate by organomagnesium compounds with the magnesiumnitrogen bond was carefully studied and a number of new catalysts were disclosed. The stereostructure of the resulting polymer as well as the catalytic activity is quite different depending on the amide group in the catalyst. The organomagnesium compounds with a piperidine ring such as ethylpentamethyleniminomagnesium or bispentamethylenimino)magnesium are found to be an effective catalyst for the syndiotactic polymerization of methyl methacrylate. The polymerization is affected by the polymerization conditions such as temperature and the solvent employed. The lower the polymerization temperature, the higher the syndiotacticity of the polymer, and toluene is a best solvent in the syndiotactic polymerization. On the other hand, organomagnesium compounds with a pyrasole ring such as ethylvinyleniminomagnesium, or bis(divinylenimino)magnesium are the novel catalyst for the isotactic polymerization of methyl methacrylate. The isotacticity of polymer is not affected by the polymerization conditions such as polymerization temperature and the solvent employed and the polymers obtained by these catalysts have all 100% isotactic units. The mechanism of the polymerization was discussed in considerable detail in view of the aggregation of the catalyst and a reasonable mode of polymerization is proposed that the propagation occurs at magnesium-nitrogen bond, and the propagation is affected by another coordinated nitrogen-bridged group in the catalyst throughout the polymerization. ince the pioneering works by Fox, et a!.,1 Miller, et al.,'1 and Watanabe, et al.,* who independently succeeded in the preparation of the stereoregular poly-(methyl methacrylate) in 1958, considerable literature on the syntheses and characterization of the stereoregular poly(methyl methacrylate) has appeared.4-10

Controlled polyethylene chain growth on magnesium catalyzed by lanthanidocene: A living transfer polymerization for the synthesis of higher dialkyl-magnesium

“…In our case, block copolymerisations were run starting from polyethylenyl lanthanide and magnesium mixtures with methyl methacrylate and with 3-caprolactone. For methyl methacrylate, the experimental conditions of the second polymerization step have been chosen by analogy with published procedures of living anionic polymerization initiated with magnesium alkyls [39]. As can be seen in run 27 (Table 5), the molecular weight enhancement between the first block and the final product is consistent with the bonding of the two polymers (Fig.…”

Stereoregulation of methyl methacrylate polymerization

“…The situation is similar with phenyl-and mesitylenylmagnesium (MsMg) initiators. Bis(diviny1enimino)magnesium yields it-PMMA in both toluene and THF but it is not a soluble initiator (Joh and Kotake, 1970).…”

“…For reference the triad frequencies of PMMA prepared in ethyl acetate at four temperatures (Bovey, 1960) are shown in Figure 3. There are two cases where an inverting chiral center may be involved: bis-(pentamethy1enimino)magnesium in THF or toluene at 195 K: i = 0, h = 0.07, s = 0.93 (Joh and Kotake, 1970) and triphenylmethylcalcium chloride in 1,2-dimethoxyethane (trace THF) at 210 K: i = 0, h = 0.12, s = 0.88 (Lindsell, 1981 al., 1965). We have tested the first of these 3 recipes but were unable to produce s contents in excess of 0.68 (Hagias, 1984).…”

Stereospecific Polymerization of Methacrylates with Ethylmagnesium Alkoxides

“…The stereospecific polymerization of ethyl, tert-butyl, a-methylbenzyl, and a, a-dimethylbenzyl methacrylates was also investigated with iso-BuOMgEt and t-BuOMgEt in toluene at -78°C. The structure of the catalysts was investigated by means of the 1 H NMR method.KEY WORDS Stereospecific Polymerization / Diethylmagnesium / Ethylmagnesium Alkoxide / Methyl Methacrylate / Methacrylate / Tacticity / Anionic Polymerization / Many organomagnesium compounds such as dialkylmagnesium (RMgR), 1 ' 2 alkylmagnesium amide (RMgNR'R"), 3 and Grignard reagent (RMgX) 1 ' 2 have been used as stereospecific catalysts for the polymerization of methacrylic esters. These compounds possess Mg-carbon, Mgnitrogen, and Mg-halide bonds, respectively, in addition to the Mg-carbon bond.…”

“…Many organomagnesium compounds such as dialkylmagnesium (RMgR), 1 ' 2 alkylmagnesium amide (RMgNR'R"), 3 and Grignard reagent (RMgX) 1 ' 2 have been used as stereospecific catalysts for the polymerization of methacrylic esters. These compounds possess Mg-carbon, Mgnitrogen, and Mg-halide bonds, respectively, in addition to the Mg-carbon bond.…”