Anionic Polymerization of Vinyl Monomers

1975 ◽  
Vol 48 (3) ◽  
pp. 359-409 ◽  
Author(s):  
Maurice Morton ◽  
Lewis J. Fetters
Keyword(s):  
Special Reference ◽  
Anionic Polymerization ◽  
Alkali Metals ◽  
Good Reason ◽  
Free State ◽  
Vinyl Monomers ◽  
Experimental Conditions ◽  
Group I ◽  
Sodium And Potassium

Abstract Addition polymerizations involving soluble organometallic species have received intensive attention in recent years with special reference to the type of counterion and solvent. An anionic mechanism is proposed for those systems where there is good reason to assume that the metal is strongly electropositive relative to the carbon (or other) atom at the tip of the growing chain. Hence, the metal, e.g. lithium, becomes a cation either in the free state or coupled with the growing carbanion. Under the appropriate experimental conditions, spontaneous termination is avoidable in many of those systems when one of the metals of Group I is used as the counterion. The alkali metals sodium and potassium were revealed to be polymerization initiators of isoprene in the disclosures of Matthews and Strange in 1910 and Harries in 1911. The first unambiguous report of the use of lithium in reactions with diolefins appears to be that of Ziegler and coworkers in 1934. Their work consisted of an investigation of the reaction between the alkali metals (lithium, sodium) or alkyllithium species and butadiene, isoprene, 2,3-dimethylbutadiene, or piperylene.

THE ELECTRONIC SPECTRA OF SOME ANIONIC POLYMERIZATION SYSTEMS

1964 ◽  
Vol 42 (6) ◽  
pp. 1255-1260 ◽  
Author(s):  
S. Bywater ◽  
A. F. Johnson ◽  
D. J. Worsfold
Keyword(s):  
Alkali Metal ◽  
Absorption Spectra ◽  
Anionic Polymerization ◽  
Electronic Spectra ◽  
Alkali Metals ◽  
Ultraviolet Absorption ◽  
Tetrahydrofuran Solution ◽  
Sodium And Potassium

The ultraviolet absorption spectra of living anionic polymerizing systems have been measured with sytrene, butadiene, and isoprene as the monomers; with lithium, sodium, and potassium as the alkali metals; and with tetrahydrofuran, cyclohexane, and benzene as the solvents. For any monomer the similarity of the spectra obtained with the various metals and solvents leads to the conclusion that the alkali metal – carbon band has the same structure under the various conditions. From other evidence the bond is considered to be ionic in all cases. The diene monomer anions in tetrahydrofuran solution were found to undergo a series of isomerizations, some of them comparable in speed to the consumption of monomer.

scholarly journals Anionic Polymerization of Vinyl Monomers with Organometallic Compound—Phosphoramide Systems

1975 ◽  
Vol 7 (3) ◽  
pp. 372-381 ◽  
Author(s):  
Masao Tomoi ◽  
Teruo Onozawa ◽  
Kenji Seki ◽  
Hiroshi Kakiuchi
Keyword(s):  
Anionic Polymerization ◽  
Organometallic Compound ◽  
Vinyl Monomers

scholarly journals Emission of Noble Gases Binary Mixtures under Excitation by the Products of the 6Li (n, α)3 H Nuclear Reaction

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Kuanysh Samarkhanov ◽  
Mendykhan Khasenov ◽  
Erlan Batyrbekov ◽  
Inesh Kenzhina ◽  
Yerzhan Sapatayev ◽  
...  
Keyword(s):  
Nuclear Reaction ◽  
Nuclear Energy ◽  
Alkali Metals ◽  
Nuclear Reactor ◽  
Noble Gases ◽  
Noble Gas ◽  
Direct Conversion ◽  
Reaction Products ◽  
Gas Molecules ◽  
Sodium And Potassium

The luminescence of Kr-Xe, Ar-Kr, and Ar-Xe mixtures was studied in the spectral range 300–970 nm when excited by 6Li (n, α)3 H nuclear reaction products in the core of a nuclear reactor. Lithium was deposited on walls of experimental cell in the form of a capillary-porous structure, which made it possible to measure up to a temperature of 730 K. The temperature dependence of the radiation intensity of noble gas atoms, alkali metals, and heteronuclear ionic noble gas molecules was studied. Also, as in the case of single-component gases, the appearance of lithium lines and impurities of sodium and potassium is associated with vaporization during the release of nuclear reaction products from the lithium layer. The excitation of lithium atoms occurs mainly as a result of the Penning process of lithium atoms on noble gas atoms in the 1s states and subsequent ion-molecular reactions. Simultaneous radiation at transitions of atoms of noble gases and lithium, heteronuclear ion molecules of noble gases allows us to increase the efficiency of direct conversion of nuclear energy into light.

Artificial Transmembrane Channels for Sodium and Potassium

2002 ◽  
Vol 85 (3) ◽  
pp. 219-241 ◽  
Author(s):  
Peter J. Cragg
Keyword(s):  
Ion Transport ◽  
Alkali Metals ◽  
Structural Features ◽  
Artificial System ◽  
Ion Specificity ◽  
Ion Concentrations ◽  
Transmembrane Channels ◽  
Essential Function ◽  
Membrane Spanning ◽  
Sodium And Potassium

Transport of alkali metals, particularly sodium and potassium, across cell membranes is an essential function performed by special proteins that enable cells to regulate inter- and extracellular ion concentrations with exceptional selectivity. The importance of these channel-forming proteins has led to researchers emulating of their structural features: an ion-specific filter and conduction at rates up to 108 ions per second. Synthetic helical and cyclic polypeptides form channels, however, the specificity of ion transport is often low. Ion-specific macrocycles have been used as filters from which membrane-spanning derivatives have been prepared. Success has been limited as many compounds act as ion carriers rather than forming transmembrane channels. Surfactant compounds also allow ions to cross membranes but any specificity is serendipitous. Overall it seems possible to mimic either ion specificity or efficient transmembrane ion transport. The goal for the future will be to combine both characteristics in one artificial system.

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