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Volumn 32, Issue 2, 1999, Pages 411-422

Modeling insight into the diffusion-limited cause of the gel effect in free radical polymerization

Author keywords

[No Author keywords available]

Indexed keywords

COMPOSITION EFFECTS; DIFFUSION IN LIQUIDS; FREE RADICAL POLYMERIZATION; MATHEMATICAL MODELS; MOLECULAR STRUCTURE; MONOMERS; OLIGOMERS;

EID: 0032760619     PISSN: 00249297     EISSN: None     Source Type: Journal    
DOI: 10.1021/ma9811324     Document Type: Article
Times cited : (87)

References (85)
  • 8
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    • note
    • Some free volume theories provide a basis (related to relative amounts of polymer and solvent or monomer) for handling, directly or indirectly, the temperature and polymer concentration dependencies of the monomeric friction coefficient, which in turn are related to the temperature and concentration dependencies of diffusion in polymer solutions such as those found in free radical polymerizations. Thus, in the more sophisticated forms, free volume theories can be more than fitting functions as they can address, with the use of meaningful physical parameters, issues of broad ranging importance in polymer physics in addition to phenomena in polymerization processes.
  • 42
    • 85034550332 scopus 로고    scopus 로고
    • note
    • With this approach the fact that the polymer concentration dependence of monomer diffusion is a strong function of temperature is already taken into account. This effect is significant as evidenced by the following example calculated using the predictive Vrentas-Duda free volume theory: for 50 wt % PMMA in MMA, MMA diffusivity at 85 °C is reduced to 25% of its value in neat MMA while at 40 °C it is reduced to about 10% of its value in neat MMA.
  • 43
    • 85034539884 scopus 로고    scopus 로고
    • note
    • Here we are speaking specifically of chain-end segmental mobility which is related to although not absolutely identical the segmental mobility associated with interior segments of a polymer chain.
  • 53
    • 0037660594 scopus 로고
    • While the phenomenon of a temperature rise accompanying the gel effect in systems without absolutely optimal heat transfer has been known for over 50 years (for examples, see ref 1 and see: Schulz, G. V.; Blaschke, F. Z. Phys. Chem. 1942, B51, 75.), this point was seemingly lost in some of the important litertature that followed, leading some researchers to model nonisothermal experimental data as if they were isothermal. Work published in 1987 (ref 50) and 1990 (O'Driscoll, K. F.; Huang, J. Eur. Polym. J. 1990, 25, 629) made clear that normal ampule polymerizations would often suffer from the effects of nonisothermality near and in the gel effect regime.
    • (1942) Z. Phys. Chem. , vol.B51 , pp. 75
    • Schulz, G.V.1    Blaschke, F.2
  • 54
    • 0024886079 scopus 로고
    • While the phenomenon of a temperature rise accompanying the gel effect in systems without absolutely optimal heat transfer has been known for over 50 years (for examples, see ref 1 and see: Schulz, G. V.; Blaschke, F. Z. Phys. Chem. 1942, B51, 75.), this point was seemingly lost in some of the important litertature that followed, leading some researchers to model nonisothermal experimental data as if they were isothermal. Work published in 1987 (ref 50) and 1990 (O'Driscoll, K. F.; Huang, J. Eur. Polym. J. 1990, 25, 629) made clear that normal ampule polymerizations would often suffer from the effects of nonisothermality near and in the gel effect regime.
    • (1990) Eur. Polym. J. , vol.25 , pp. 629
    • O'Driscoll, K.F.1    Huang, J.2
  • 55
    • 0000353913 scopus 로고
    • t values. See, for example, refs 26 and 27 and the following: Mahabadi, H. K. Macromolecules 1985, 18, 1319; Mahabadi, H. K. Macromolecules 1991, 24, 606. Matsumoto, A.; Mizuta, K. Macromolecules 1994, 27, 1657. Wisnudel, M. B. Ph.D. Dissertation, Northwestern University, 1996.
    • (1985) Macromolecules , vol.18 , pp. 1319
    • Mahabadi, H.K.1
  • 56
    • 0025802191 scopus 로고
    • t values. See, for example, refs 26 and 27 and the following: Mahabadi, H. K. Macromolecules 1985, 18, 1319; Mahabadi, H. K. Macromolecules 1991, 24, 606. Matsumoto, A.; Mizuta, K. Macromolecules 1994, 27, 1657. Wisnudel, M. B. Ph.D. Dissertation, Northwestern University, 1996.
    • (1991) Macromolecules , vol.24 , pp. 606
    • Mahabadi, H.K.1
  • 57
    • 0028388492 scopus 로고
    • t values. See, for example, refs 26 and 27 and the following: Mahabadi, H. K. Macromolecules 1985, 18, 1319; Mahabadi, H. K. Macromolecules 1991, 24, 606. Matsumoto, A.; Mizuta, K. Macromolecules 1994, 27, 1657. Wisnudel, M. B. Ph.D. Dissertation, Northwestern University, 1996.
    • (1994) Macromolecules , vol.27 , pp. 1657
    • Matsumoto, A.1    Mizuta, K.2
  • 58
    • 18644370519 scopus 로고    scopus 로고
    • Ph.D. Dissertation, Northwestern University
    • t values. See, for example, refs 26 and 27 and the following: Mahabadi, H. K. Macromolecules 1985, 18, 1319; Mahabadi, H. K. Macromolecules 1991, 24, 606. Matsumoto, A.; Mizuta, K. Macromolecules 1994, 27, 1657. Wisnudel, M. B. Ph.D. Dissertation, Northwestern University, 1996.
    • (1996)
    • Wisnudel, M.B.1
  • 60
    • 85034558993 scopus 로고    scopus 로고
    • note
    • The temperature dependence of monomer diffusion in polymermonomer solutions has received little study. However, ref 66 provides limited data for MMA diffusion as a function of PMMA concentration at -10 and +50 °C. Additionally, detailed information regarding the quantitative effects of temperature on small-molecule probe diffusion in polymer solutions is found in ref 38.
  • 61
    • 85034555658 scopus 로고    scopus 로고
    • note
    • t at any given temperature is fundamentally and only due to free volume effects.
  • 62
    • 85034536415 scopus 로고    scopus 로고
    • note
    • t to be significantly weaker than that of monomer diffusion.) Instead, it is that the simple model described here, which does not account for effects of chain transfer in slowing the rate of polymerization through behavior akin to retardation or inhibition, is inadequate to model quantitatively the early to middle stages of the gel effect in bulk styrene free radical polymerization.
  • 63
    • 18644369079 scopus 로고    scopus 로고
    • Ph.D. dissertation, Northwestern Universtiy
    • O'Neil, G. A. Ph.D. dissertation, Northwestern Universtiy, 1998.
    • (1998)
    • O'Neil, G.A.1
  • 65
    • 85034548555 scopus 로고    scopus 로고
    • note
    • t may be increased (relative to the case of no chain transfer) due to the presence of a significantly higher level of short oligomeric radical chains deriving from chain transfer reactions.
  • 66
    • 0027113846 scopus 로고
    • x,m parameter (it is expressed somewhat differently in the 1992 reference) having a molecular weight independent value of 1.50 for MMA and 1.57 for styrene, an assumption not supported by the results presented in this paper. To provide approximate fits under these circumstances, the simulations from this complex model consistently overestimated MMA conversions up to fractional conversions of 0.4, in some cases significantly overestimating the onset conversion of the gel effect.
    • (1992) Macromolecules , vol.25 , pp. 3739
    • Achillas, D.S.1    Kiparassides, C.2
  • 72
    • 85034535408 scopus 로고    scopus 로고
    • note
    • t to be significantly weaker than that of monomer diffusion.) Instead, it is that the simple model described here, which does not account for effects of chain transfer (in these cases due to addition of dodecanethiol) in slowing the rate of polymerization through behavior akin to retardation or inhibition, is inadequate to model quantitatively the early to middle stages of the gel effect in bulk MMA free radical polymerization when substantial amounts of chain transfer agent are present.
  • 75
    • 85034541580 scopus 로고    scopus 로고
    • note
    • We do not discount that other reasons besides chain transfer (with some related retardation and inhibition effects) contribute to the apparently mild gel effect observed in isothermal, bulk styrene polymerization. However, we as yet have no support for other causes.
  • 76
    • 85034562613 scopus 로고    scopus 로고
    • note
    • x,m increases only slightly. (See Table 3.) Nevertheless, further study will be needed to determine conditions where this issue may be of some quantitative importance, well outside the range of experimental error.
  • 83
    • 85034543316 scopus 로고    scopus 로고
    • note
    • -4T (°C) in ref 14. The results in ref 14 were in fact determined using the correct value of ε listed here in Table 2.
  • 85
    • 85034557603 scopus 로고    scopus 로고
    • note
    • t are of key importance in the analysis provided in this manuscript.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.