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Volumn 80, Issue 2, 2007, Pages 439-452

Mechanistic analysis and thermochemical kinetic simulation of the products from pyrolysis of poly(α-methylstyrene), especially the unrecognized role of phenyl shift

Author keywords

Computational modeling; Phenyl shift; Poly( methylstyrene); Pyrolysis; Radical mechanisms

Indexed keywords

AROMATIC COMPOUNDS; COMPUTER SIMULATION; MOLECULAR WEIGHT; PYROLYSIS; REACTION KINETICS;

EID: 34548249633     PISSN: 01652370     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.jaap.2007.05.005     Document Type: Article
Times cited : (14)

References (101)
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    • Early work is reviewed in S.L. Madorsky, Interscience, New York
    • Early work is reviewed in S.L. Madorsky. Thermal Degradation of Organic Polymers (1964), Interscience, New York
    • (1964) Thermal Degradation of Organic Polymers
  • 6
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    • note
    • Decomposition in solution or as part of mixtures with other polymers is not reviewed in detail, but selected data will be used in mechanistic considerations.
  • 24
    • 34548247459 scopus 로고    scopus 로고
    • 12, a dimethylnaphthalene, bibenzyl, and two methylstilbenes were claimed; from the portrayed spectrum, the most prevalent were the minor amounts of toluene and styrene, while the others were trivial compared with αMS. For 1-h runs at increasing T in hydrogen donor solvents in a sealed autoclave (Ref. [16]), a secondary conversion of αMS to cumene and ethylbenzene was clearly demonstrated.
  • 30
    • 0009987067 scopus 로고
    • (the text and the graphic in this report are not consistent)
    • Fares M.M., Yalcin T., Hacaloglu J., Gungor A., and Suzer S. Analyst 119 (1994) 693 (the text and the graphic in this report are not consistent)
    • (1994) Analyst , vol.119 , pp. 693
    • Fares, M.M.1    Yalcin, T.2    Hacaloglu, J.3    Gungor, A.4    Suzer, S.5
  • 35
    • 34548278156 scopus 로고    scopus 로고
    • For an early exception that gave sigmoidal plots of %wt. loss versus t, see Ref. [20b].
  • 36
    • 34548257529 scopus 로고    scopus 로고
    • -1.
  • 37
    • 34548255152 scopus 로고    scopus 로고
    • -1.
  • 41
    • 34548252665 scopus 로고    scopus 로고
    • note
    • Similar trends were reported by Richards and Salter (Ref. [28]) for mixtures of PαMS and PS.
  • 43
    • 34548217983 scopus 로고    scopus 로고
    • n0.
  • 44
    • 34548285634 scopus 로고    scopus 로고
    • note
    • n < 1.1.
  • 45
    • 34548225216 scopus 로고    scopus 로고
    • note
    • n0 range (3100-71,000) and a greater range of initial polydispersity; cf. Ref. [29].
  • 46
    • 34548238969 scopus 로고    scopus 로고
    • note
    • w vs. t at 350 °C are also available [12a] for low-M starting polymer.
  • 47
    • 34548267891 scopus 로고    scopus 로고
    • note
    • The analogous distributions at 10 °C lower T were significantly different, and the authors noted that the latter T coincided with the fusion T range of high-M PαMS.
  • 48
    • 34548226220 scopus 로고
    • Certain features of the data, especially for the cationic sample, such as x vs. t plots that plateau at quite low x values, appear atypical and raise questions whether the cationic sample suffered from some unknown inhibition effect
    • Braun D., and Heufer G. Makromol. Chem. 79 (1964) 98 Certain features of the data, especially for the cationic sample, such as x vs. t plots that plateau at quite low x values, appear atypical and raise questions whether the cationic sample suffered from some unknown inhibition effect
    • (1964) Makromol. Chem. , vol.79 , pp. 98
    • Braun, D.1    Heufer, G.2
  • 50
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    • note
    • Jellinek and Luh (Ref. [20c]) proposed termination between a polymeric radical and monomer, but the reaction envisioned was not specified.
  • 51
    • 34548203645 scopus 로고    scopus 로고
    • note
    • Some authors, e.g., Refs. [7,9a,16,25,28], have implied that no transfer occurs.
  • 52
    • 34548210177 scopus 로고    scopus 로고
    • note
    • Escape of small radicals from the melt by volatilization has been considered; cf. Ref. [28].
  • 53
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  • 56
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    • 2 = 0; however, the other two pairs are not mutually exclusive.
  • 57
    • 34548225215 scopus 로고    scopus 로고
    • rxn.
  • 65
    • 34548265433 scopus 로고    scopus 로고
    • note
    • We have done so for the analogous PIB in Ref. [2b].
  • 67
    • 34548282348 scopus 로고    scopus 로고
    • note
    • Z′ also differs somewhat from Z in that the classical mechanism in steps (1)-(10) does not consider the transfer that must accompany BB-outward.
  • 68
    • 34548280629 scopus 로고    scopus 로고
    • n0 data pair.
  • 73
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    • -1 higher energy).
  • 74
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    • Such "size" estimates are of course crude statements, dependent on the system involved, as illustrated by the example in which 1-methyl-1-phenylcyclohexane prefers to have the phenyl group axial even though the equatorial preference in the mono-substituted cyclohexanes is larger for the phenyl group
    • Such "size" estimates are of course crude statements, dependent on the system involved, as illustrated by the example in which 1-methyl-1-phenylcyclohexane prefers to have the phenyl group axial even though the equatorial preference in the mono-substituted cyclohexanes is larger for the phenyl group. Wiberg K.B., Castejon H., Bailey W.F., and Ochterski J. J. Org. Chem. 65 (2000) 1181
    • (2000) J. Org. Chem. , vol.65 , pp. 1181
    • Wiberg, K.B.1    Castejon, H.2    Bailey, W.F.3    Ochterski, J.4
  • 75
    • 34548243825 scopus 로고    scopus 로고
    • note
    • A rather complete set of rate constant assignments was presumably made by the Broadbelt group (Ref. [12a]) but the values were not explicitly given.
  • 76
    • 85058923827 scopus 로고    scopus 로고
    • H(p, s).
  • 78
    • 34548221213 scopus 로고    scopus 로고
    • note
    • An estimate based on similar hydrocarbon polymers; no data was found for PαMS.
  • 79
    • 34548251206 scopus 로고    scopus 로고
    • p{radical dot}.
  • 81
    • 34548248894 scopus 로고    scopus 로고
    • -1, respectively, are not different within experimental error.
  • 82
    • 34548215422 scopus 로고    scopus 로고
    • p{radical dot} model 2,4,6-methyl-2,4,6-triphyenyl-1-heptyl (average for diastereomers).
  • 83
    • 34548212126 scopus 로고    scopus 로고
    • See Ref. [7] in Ref. [2b].
  • 84
    • 34548247962 scopus 로고    scopus 로고
    • β(tb, tb).
  • 85
    • 34548258537 scopus 로고    scopus 로고
    • Repeating the simulation for 250 °C with use of the unaltered rate constant assignments used for PE (Ref. [2a]), i.e., with no adjustments for the special steric factors in PαMS, predicted > 99% RS and only 1 wt.% αMS among the volatiles, outputs much further in the "wrong" direction.
  • 86
    • 34548209474 scopus 로고    scopus 로고
    • For leading references on 1,2-phenyl shift see Ref. [2c]; a parallel 1,2-methyl shift would of course be unprecedented.
  • 90
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    • -1 has been reported but the authors questioned this higher A value
    • -1 has been reported but the authors questioned this higher A value
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    • Weber, M.1    Fischer, H.2
  • 91
    • 34548200554 scopus 로고    scopus 로고
    • There is a paucity of models for 1,x-shifts involving tert centers (Ref. [46]).
  • 93
    • 34548288282 scopus 로고    scopus 로고
    • i would need to address the tacticity surrounding the C-C bond being homolyzed. There has been a suggestion (Ref. [34]) that an isotactic triad will be more sterically compressed and hence possibly more prone to homolysis.
  • 96
    • 34548233995 scopus 로고    scopus 로고
    • -1) used and their sources were: t-butylbenzene, -5.5 (experimental value from Refs. [71] and [72]; t-amylbenzene, -9.6 (estimated values of -9.9 by GA and -10.2 by GMMX, adjusted by the difference for t-butylbenzene between the experimental value of -5.5 and estimated values of -5.8 (GA) and -6.0 (GMMX)); cumyl, 32.0 (recommended value in Ref. [72]); methyl, 35.1 (recommended value in Ref. [71]); and ethyl, 28.4 (recommended value in Ref. [72]).
  • 97
    • 34548278654 scopus 로고    scopus 로고
    • NIST Chemistry WebBook, Standard Reference Database Number 69, June, 2005 Release (http://webbook.nist.gov).
  • 98
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    • In: Lide D.R. (Ed). CRC Handbook of Chemistry and Physics. 87th ed. (2006), Taylor and Francis, Boca Raton, FL. http://www.hbcpnetbase.com/ Internet version (http://www.hbcpnetbase.com)
    • (2006) CRC Handbook of Chemistry and Physics. 87th ed.
  • 99
    • 34548280122 scopus 로고    scopus 로고
    • This fraction is based on the suggestion of Ruchardt and Beckhaus (Ref. [67]) that, for series of internally strained molecules, an increase in strain energy decreases E by only ≈2/3 because of the compensation by a growing barrier to recombination.


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