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Volumn 33, Issue 7, 2000, Pages 2320-2334

Synthesis of branched polyethylene using (a-diimine)nickel(ii) catalysts: Influence of temperature, ethylene pressure, and ligand structure on polymer properties

Author keywords

[No Author keywords available]

Indexed keywords

CATALYST DEACTIVATION; COMPOSITION; MICROSTRUCTURE; MOLECULAR STRUCTURE; MOLECULAR WEIGHT; NICKEL COMPOUNDS; ORGANOMETALLICS; POLYMERIZATION; PRESSURE EFFECTS; SYNTHESIS (CHEMICAL); THERMAL EFFECTS;

EID: 0033750251     PISSN: 00249297     EISSN: None     Source Type: Journal    
DOI: 10.1021/ma991234+     Document Type: Article
Times cited : (780)

References (74)
  • 1
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    • See for example
    • See for example:
  • 17
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    • Following initial discoveries at UNO, collaborative efforts were initiated with the group at DuPont.
    • Johnson, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem. Soc. 1995, 117, 6414. Following initial discoveries at UNO, collaborative efforts were initiated with the group at DuPont.
    • (1995) J. Am. Chem. Soc. , vol.117 , pp. 6414
    • Johnson, L.K.1    Killian, C.M.2    Brookhart, M.3
  • 44
    • 0027113187 scopus 로고
    • 1,3-Enchainment in polymerizations of cyclopentene has previously been observed for early metal metallocene catalysts. See: Collins, S.; Kelly, W. M. Macromolecules 1992, 25, 233.
    • (1992) Macromolecules , vol.25 , pp. 233
    • Collins, S.1    Kelly, W.M.2
  • 49
    • 0033605733 scopus 로고    scopus 로고
    • 13C NMR spectroscopic and light scattering studies have shown that the polyethylene produced with (a-diimine)palladium(II) catalysts is hyperbranched. See ref 9 and: Guan, Z.; Cotts, P. M.; McCord, E. F.; McLain, S. J. Science 1999, 283, 2059.
    • (1999) Science , vol.283 , pp. 2059
    • Guan, Z.1    Cotts, P.M.2    McCord, E.F.3    McLain, S.J.4
  • 56
    • 33745572913 scopus 로고    scopus 로고
    • Due to the high activity of these catalysts, even under conditions of high dilution and low catalyst loadings, the consumption of monomer is very rapid, and the catalyst rapidly becomes starved for monomer.
    • Due to the high activity of these catalysts, even under conditions of high dilution and low catalyst loadings, the consumption of monomer is very rapid, and the catalyst rapidly becomes starved for monomer.
  • 57
    • 33745572927 scopus 로고    scopus 로고
    • Turnover frequency (TOF) is calculated as the moles of ethylene consumed per mole of catalyst used per unit of time (h).
    • Turnover frequency (TOF) is calculated as the moles of ethylene consumed per mole of catalyst used per unit of time (h).
  • 58
    • 33745539991 scopus 로고    scopus 로고
    • It is also possible that the 2,6-disubstituted aryl groups undergo slow rotation in solution, however on the time scale of the polymerization reactions, it is likely that these groups are fixed either in the Ci or C, conformations.
    • It is also possible that the 2,6-disubstituted aryl groups undergo slow rotation in solution, however on the time scale of the polymerization reactions, it is likely that these groups are fixed either in the Ci or C, conformations.
  • 59
    • 33745566657 scopus 로고    scopus 로고
    • Turnover frequencies given assume complete catalyst activation. Recent results suggest initial reaction with methylaluminoxane may produce some inactive nickel materials: Gates, D. P.; Brookhart, M. Unpublished results.
    • Turnover frequencies given assume complete catalyst activation. Recent results suggest initial reaction with methylaluminoxane may produce some inactive nickel materials: Gates, D. P.; Brookhart, M. Unpublished results.
  • 60
    • 33745524774 scopus 로고    scopus 로고
    • Ph.D. Thesis, University of North Carolina at Chapel Hill
    • Killian, C. M. Ph.D. Thesis, University of North Carolina at Chapel Hill, 1996.
    • (1996)
    • Killian, C.M.1
  • 61
    • 33745569595 scopus 로고    scopus 로고
    • note
    • The branching numbers determined by 1H NMR give no information about the types of branches (i.e., methyl, ethyl, propyl), A series of multidimensional NMR experiments conducted by E. M. McCord on polyethylene produced from nickel diimine catalysts indicate the frequency of branching to be Me > Et > Pr > Bu, etc. See ref 9.
  • 62
    • 84982071317 scopus 로고
    • + complexes in solution: Johnson, L. K.; Tempel, D. J.; Brookhart, M. Unpublished results.
    • + complexes in solution: Johnson, L. K.; Tempel, D. J.; Brookhart, M. Unpublished results.
    • (1976) Chem. Ber. , vol.109 , pp. 1657
    • Torn Dieck, H.1    Svoboda, M.2
  • 63
    • 33745526623 scopus 로고    scopus 로고
    • Monomer flow measurements using ortho alkyl-substituted catalysts 40 was attempted for comparative purposes; however, the data were unreliable because the polyethylene formed is not very soluble in the reaction solution. The reaction mixture becomes heterogeneous in less than 30 min and thus long-term flow data are inconsistent.
    • Monomer flow measurements using ortho alkyl-substituted catalysts (40 was attempted for comparative purposes; however, the data were unreliable because the polyethylene formed is not very soluble in the reaction solution. The reaction mixture becomes heterogeneous in less than 30 min and thus long-term flow data are inconsistent.
  • 64
    • 33745522333 scopus 로고    scopus 로고
    • m's without also considering (i) the type of branching present and (ii) the shape of the melt endotherm. For example in Table 3 (entries 23 and 24), polymers prepared with catalyst 6 at 400 and 600 psig, respectively, show similar Tm's and branching numbers.
    • m's without also considering (i) the type of branching present and (ii) the shape of the melt endotherm. For example in Table 3 (entries 23 and 24), polymers prepared with catalyst 6 at 400 and 600 psig, respectively, show similar Tm's and branching numbers but inspection of the DSC thermograms show that the shapes of the melt transitions are quite different (entry 23 being much broader than entry 24). It becomes even more difficult to quantitatively compare branching vs Tm for polymers prepared using different catalysts. For example, catalyst 4f at 200 and 400 psig (35 °C) yields polymers with 13 and 12 branches respectively (Table 3 entries 13 and 14) and catalyst 5 at 400 and 600 psig (35 C) yields polymers with 11 branches (Table 5, entries 20 and 21), yet despite similar branching numbers, TVs are 128 and 126 C for polymers from catalyst 4f and 108 and 114 C for polymers from catalyst 5. Of course, the shapes of the melt curves are remarkably different. What is clear from the data is that, in general, the larger the branching number the lower the Tm and that the properties of the polyethylenes produced are highly sensitive to both the nature of the catalyst and the conditions under which the polymerizations are carried out.
  • 74
    • 33745551037 scopus 로고    scopus 로고
    • note
    • Full details of the determination of the X-ray crystal structures of 4c and 4d have been deposited with the Cambridge Crystallographic Centre. The coordinates can be obtained, on request, from the Director, Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, U.K. (CCDC129234 and CCDC129234, respectively).


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.