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  • metallocene catalyst  (2)
  • trityl tetrakis(pentafluorophenyl)borate  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Olefin terpolymerizations. II. 4-vinylcyclohexene and cyclooctadiene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2787-2793 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Ziegler-Natta catalysis ; EPDM synthesis ; metallocene catalyst ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 4-Vinylcyclohexene (VCH) and cyclooctadiene (COD) were investigated as termonomers in EPDM (ethylene/propylene/diene) synthesis by using rac-ethylenebis (1-η5-indenyl) zir-conium dichloride (1) as a catalyst precursor. Homopolymerizations of VCH, vinylcycloh-exane and cyclohexene were compared. The parameter Kπκp, which is the apparent rate constant for Ziegler-Natta polymerization, is about the same for VCH and vinylcyclohexanebut is 10 times smaller for cyclohexene. Therefore, the linear olefinic double bond is more active than the cyclic internal double bond. VCH reduces ethylene polymerization rate but not propylene polymerization rate in copolymerizations. In terpolymerizations, VCH tends to suppress ethylene incorporation especially at elevated polymerization temperature and Lowers the polymer MW by about two-fold. COD has very low activity as a termonomer. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1995.080331612
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  • 2
    Digitale Medien
    Digitale Medien
    Olefin terpolymerizations. III. Symmetry, sterics, and monomer structure in ansa-zirconocenium catalysis of EPDM synthesis (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2795-2801 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Ziegler-Natta catalysis ; EPDM synthesis ; metallocene catalyst ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ethylenebis (η5-fluorenyl) zirconium dichloride (1) and rac-dimethylsilylene bis (1-η5-in-denyl) zirconium dichloride (2) were activated with methylaluminoxane (MAO) to catalyze ethylene (E) propylene (P) copolymerizations. The former produces high MW copolymer at 20°C rich in ethylene with reactivity ratio values of rE = 1.7 and rP 〈0.01, whereas the latter produces lower MW random copolymers with rE = 1.32 and rp = 0.36. Ethylidene norbornene (ENB) complexes with 1/MAO but does not undergo insertion in the presence of E and P. In contrast, 2/MAO catalyzes terpolymerization incorporating 9-15 mol % of ENB with slightly lower MW and activity than the corresponding copolymerizations. In comparison, 1,4-hexadiene was incorporated by 2/MAO with much lower A and MW. Terpolymerizations were also conducted with vinylcyclohexene using both catalyst systems. The steric and electronic effects in these processes were discussed. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1995.080331613
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  • 3
    Digitale Medien
    Digitale Medien
    (η5-Pentamethylcyclopentadienyl)trimethyltitanium as a precursor for the syndiospecific polymerization of styrene (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 393-396 
    Details
    ISSN: 0268-2605
    Schlagwort(e): Polystyrene ; syndiotactic ; syndioselective ; MAO ; cationic catalysts ; trityl tetrakis(pentafluorophenyl)borate ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An equimolar mixture of Cp*Ti(CH3)3 (2) and Ph3C+[B(C6F5)4]- (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 × 107 g PS (mol Ti)-1 (mol styrene)-1 h-1. Both activity and syndioselectivity can be increased using tri-isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl3/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aoc.590080413
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  • 4
    Digitale Medien
    Digitale Medien
    Low-temperature isospecific polymerization of propylene catalyzed by alkylzirconocene-type ‘cations’ (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 7 (1993), S. 71-74 
    Details
    ISSN: 0268-2605
    Schlagwort(e): Polypropylene ; polymerization ; isospecificity ; alkylzirconocene-type cations ; stereoselectivity ; MAO ; cationic catalysts ; trityl tetrakis(pentafluorophenyl)borate ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rac-ethylenebis(indenyl)methylzirconium ‘cation’ (1), generated from rac-Et(Ind)2ZrMe2 and Ph3CB(C6F5)4, has recently been shown to be exceedingly active and stereoselective in propylene polymerization. The ethyl analog (2) can be produced by an alternate, efficient route involving a reaction between rac-Et(Ind)2ZrCl2 and AlEt3 (TEA), followed by addition of Ph3CB(C6F5)4. The use of excess AlEt3 serves both to alkylate the zirconium complex as well as to scavenge the system. The propylene polymerization activity of the ‘cation’ 2 is about 7000 times greater than the activity of rac-Et(Ind)2ZrCl2/methylaluminoxane (MAO) at Tp=-20°C. The related catalyst system rac-Me2Si(Ind)2ZrCl2/TEA/Ph3CB(C6F5)4 (3) was found to produce 98.3% i-PP with Tm 156.3°C and an activity of 1.8 × 109 g PP {(mol Zr) [C3H6]h}-1.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aoc.590070109
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