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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of highly isotactic (mm 〉 0.70) polyacrylonitrile by anionic polymerization using diethylberyllium as a main initiator (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 207-213 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; diethylberyllium ; additive ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to synthesize steroregular polyacrylonitrile (PAN) with a high triad isotacticity (i.e. the content of mm (m, meso)) exceeding 0.70 by the anionic polymerization method. In the stereospecific polymerization of acrylonitrile (AN) initiated by diethylberyllium (Et2Be) in xylene at 130°C, the (mm) content as well as the viscosity-average molecular weight (MÞv) of PAN increased by addition of diisobutylaluminum hydride (i-C4H9)2AlH) as an additive to the polymerization system. Maximum (mm) content, attained in the molar ratio region of (i-C4H9)2AlH/Et2Be 〉 1.0, was about 0.73. The stereospecific polymerization of AN was also initiated using a mixture of Et2Be and di-n-hexylamagnesium ((Et2Be/(n-C6H13)2 Mg system), where both Et2Be and (n-C6H13)2 Mg can induce the stereospecific polymerization of AN at 130°C. The (mm) content of the PAN sample prepared using the Et2Be/(n-C6H13)2 Mg system ((mm) = 0.64) was higher than that of PAN samples synthesized using Et2Be alone ((mm) = 0.56) and (n-C6H13)2Mg alone ((mm) = 0.51) under the same conditions except initiator. A significant difference in 13C chemical shifts of α-carbons between Et2Be (1.35 ppm) and (n-C6H13)2Mg (10.72 ppm) dissolved in hydrocarbon solvent at 110°C leads us to the conclusion that when Et2Be induces the stereospecific polymerization in the Et2Be/(n-C6H13)2Mg system as initiator, the main role of (n-C6H13)2Mg is considered to be the suppression of the association of Et2Be (active site) itself.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210350211
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of ultra-high molecular weight polyacrylonitrile with highly isotactic content (mm 〉 0.60) using dialkylmagnesium/polyhydric alcohol system as catalyst (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 87-99 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; anionic polymerization ; dialkylmagnesium ; polyhydric alcohol ; ultra-high molecular weight ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to synthesize a catalyst having high activity for synthesis of highly isotactic polyacrylonitrile (PAN) with high molecular weight by anionic polymerization. The reaction products of di-n-hexylmagnesium [(n-C6H13)2Mg] with alicyclic alcohols such as 1,4-cyclohexanediol or 1,5-decalindiol were found to be effective as polymerization catalysts for preparation of PAN samples whose triad isotacticity [the content of mm (m, meso configuration)] is about 0.64 and viscosity-average molecular weight (Mv) exceeds 1 × 105. The triad tacticities [mm, mr, and rr contents (r, racemo configuration)] of the polymers obtained were analysed by 13C NMR and their Mvs were determined by viscometry in dimethylsulphoxide at 25°C using Kamide et al.'s Mark-Houwink-Sakurada equation.Mv of PAN increased significantly by after-treatment of the catalysts, prepared from (n-C6H13)2Mg and alicyclic alcohols, with triethylalyminium (Et3Al). Ultra-high molecular weight PAN samples ranging in Mv from 2 × 106 to 6 × 106 [(mm) = 0.57-0.66] were obtained in anisole at 135°C by using the above catalyst system. A main role of Et3Al in these catalyst systems is considered to reduce, in advance, OH groups on the catalyst, resulting in a significant suppression of termination reactions of propagating PAN chains during the polymerization.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360112
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile using dialkylmagnesium as catalyst (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 34 (1994), S. 397-405 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; dialkylmagnesium ; alkylaluminum ; additive ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to clarify the effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile (AN) initiated by dialkylmagnesium (R2Mg) above 100°C. The triad isotacticity (i.e. the content of mm (m: meso)) as well as the viscosity-average molecular weight (M̄v) of polyacrylonitrile (PAN) increased when trialkylaluminum (R3Al) and trialkylboron (R3B) were used as additives. Diisobutylaluminum hydride [(i-C4H9)2AlH] was found to be the best additive. in the stereospecific polymerization of AN, giving PAN with higher (mm) content (0.63), higher M̄v value (5.2 × 104), and a yield approximately double that obtained using (n-C6H13)2Mg alone. When the (n-C6H13)2Mg/(i-C4H9)2AlH system was used, the yield, (mm), and M̄v of PAN increased with polymerization temperature (Tp); maximum values of yield, (mm), and M̄v were obtained at c. 130°C. The optimum amount of additives was approximately equimolar to R2Mg as initiator. The 13C chemical shift of α-carbon in R2Mg at 90°C shifted by mixing with R3Al and R3B, respectively, indicating the existence of interaction between R2Mg and the additives. The main role of the additives is considered to be suppression of the self-association of R2Mg by strong interaction with R2Mg.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210340408
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  • 4
    Electronic Resource
    Electronic Resource
    Highly isotactic polyacrylonitriles prepared using dialkylmagnesium/water systems as initiators (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 249-255 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; dialkylmagnesium ; alkylaluminum ; water ; high molecular weight ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to synthesize stereoregular polyacrylonitrile (PAN) with high molecular weight (e.g. viscosity-average molecular weight (M̄v) 〉 1 × 105) by anionic polymerization. The triad tacticities (i.e. the content of mm, mr and rr (m, meso; r, racemo)) of the polymers obtained were analyzed by 13C NMR and their M̄v was determined by viscometry in dimethylsulfoxide at 25°C using Kamide et al.'s Mark-Houwink-Sakurada equation. Highly isotactic and high molecular weight PAN with M̄v 〉 2.5 × 105 ((mm) ∼ 0.57) was synthesized in anisole at 130°C when the reaction product of di-n-hexylmagnesium with water supplied by heating sulfate hydrates (Na2SO4 10H2O, CuSO4 5H2O, and MgSO4 7H2O) was used as a polymerization catalyst. The M̄v of PAN was increased significantly by using the catalyst combined with triethylaluminum (Et3Al). Maximum M̄v attained was 9.7 × 105 ((mm) = 0.64). The main role of Et3Al added is explained as the reduction of OH groups in the catalyst and of residual H2O in the catalyst solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210350306
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