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
SynopsisAmorphous polyacrylonitrile was successfully synthesized with bis(pentamethy1eneimino)magnesium in heptane at 70°C. The amorphousness of the polymer increased with rising polymerization temperature and was favored by the nonpolar solvent. The polymer showed regular head-to-tail sequences which were confirmed by converting the polymer into polyacrylic acid and polymethylacrylate. The amorphous PAN produced a broad x-ray diagram with a maximum at 20 = 16.1' and a less intense halo a t 20 = 27.5'. This pattern did not change after heat treatment. The synthesis of amorphous PAN strongly supports Imai's hypothesis that polyacrylonitrile consists of paracrystalline and amorphous phases. The amorphous PAN also tends to support Minami's assignment of the two absorptions in the temperature dependence of the dynamic loss tangent; the absorption a t the lower temperature (110OC) is due to molecular motions in the paracrystalline phase and the absorption a t the higher temperature (160°C) is attributed to the molecular motions in the amorphous region.
Methacrylonitrile (MAN) was polymerized with diethylmagnesium. Acetone‐insoluble portions of the polymers are found to be crystalline. Highly crystalline portions can be isolated by further extraction of the acetone‐insoluble parts with dimethylformamide (DMF). A film of DMF‐insoluble fraction can be oriented uniaxially by hot‐press rolling. The crystalline PMAN is insoluble in the usual solvents for amorphous PMAN because of their crystallinity and is easily soluble in CF3COOH or Cl2CHCOOH. The viscosity–molecular weight relationship was determined in Cl2CHCOOH at 30°C. as [η] = 3.24 × 10−3M0.520. We found several crystalline bands in the infrared spectra, for example, at 1192 and 885 cm.−1. Formation of the carbonyl group in the polymer is discussed, and it is concluded that it may be formed by the hydrolysis of conjugated cyclic imine or hydrolysis of the nitrile group in the polymer to acid amide.
The polymerization of isobutyl vinyl ether by vanadium trichloride in n‐heptane was studied. VCl3 • LiCl was prepared by the reduction of VCl4 with stoichiometric amounts of BuLi. This type of catalyst induces stereospecific polymerization of isobutyl vinyl ether without the action of trialkyl aluminum to an isotactic polymer when a rise in temperature during the polymerization was depressed by cooling. It is suggested that the cause of the stereospecific polymerization might be due to the catalyst structure in which LiCl coexists with VCl3, namely, VCl3 • LiCl or VCl2 • 2LiCl as a solid solution in the crystalline lattice, since VCl3 prepared by thermal decomposition of VCl4 and a commercial VCl3 did not produce the crystalline polymer and soluble catalysts such as VCl4 in heptane and VCl3 • LiCl in ether solution did not yield the stereospecific polymer. It was found that some additives, such as tetrahydrofuran or ethylene glycol diphenyl ether, to the catalyst increased the stereospecific polymerization activity of the catalysts. Influence of the polymerization conditions such as temperature, time, monomer and catalyst concentrations, and the kind of solvent on the formed polymer was also examined.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.