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Holder, Simon J.; Achilleos, Mariliz; Jones, Richard G. (2006)
Publisher: American Chemical Society
Languages: English
Types: Article
Subjects: Q
In this communication, we will demonstrate that polymerization in a chiral solvent can affect the molecular weight distribution of the product by perturbing the balance of the P and M helical screw senses of the growing chains. Specifically, for the Wurtz-type synthesis of polymethylphenylsilane (PMPS) in either (R) or (S)-limonene, the weight-average molecular weight of the products (average Mw = 80 000) was twice that of PMPS synthesized in (R/S)-limonene (average Mw = 39 200). Peturbation of the helical segmentation along the polymer chains leads to a reduction in the rate of occurrence of a key termination step. This the first time that a chiral solvent has been demonstrated to have such an effect on a polymerization process in affecting molecular weight parameters in contrast to affecting tacticity.
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    • (1) Baudequin, C.; Bre´geon, D.; Levillain, J.; Guillen, F.; Plaqueventand, J.- C.; Gaumont, A.-C. Tetrahedron: Asymmetry 2005, 16, 3921-3945.
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    • (3) (a) Nolte, R. J. M. Chem. Soc. ReV. 1994, 23, 11-19. (b) Okamoto, Y.; Nakano, T. Chem. ReV. 1994, 94, 349-372. (c) Green, M. M.; Peterson, N. C.; Sato, T.; Teramoto, A.; Cook, R.; Lifson, S. Science 1995, 268, 1860-1866.
    • (4) (a) Cornelissen, J. J. L. M.; Rowan, A. E.; Nolte, R. J. M.; Sommerdijk N. A. J. M. Chem. ReV. 2001, 101, 4039-4070. (b) Yashima, E.; Matsushima, T.; Okamoto, Y. J. Am. Chem. Soc. 1995, 117, 11596- 11597. (c) Havinga, E. E.; Bouman, M. M.; Meijer E. W.; Pomp, A.; Simenon, M. M. J. Synth. Met. 1994, 66, 93-97. (d) Khatri, C. A.; Pavlova, Y.; Green, M. M.; Morawetz, H. J. Am. Chem. Soc. 1997, 119, 6991-6995. (e) Green, M. M.; Khatri, C.; Peterson, N. C. J. Am. Chem. Soc. 1993, 115, 4941-4942. (f) Yashima, E.; Matsushima, T.; Okamoto, Y. J. Am. Chem. Soc. 1997, 119, 6345-6359.
    • (5) Jones, R. G.; Holder, S. J. In Silicon-based Polymers: The Science and Technology of their Synthesis and Applications; Jones, R. G., Ando, W., Chojnowski, J., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 2000; pp 353-373.
    • (6) Fujiki, M. Macromol. Rapid. Commun. 2001, 22, 539 and references therein.
    • (7) McLeish, T. C. B.; Jones R. G.; Holder, S. J. Macromolecules 2002, 35, 548-554.
    • (8) Dellaportas, P.; Holder, S. J.; Jones, R. G. Macromol. Rapid Commun. 2002, 23, 99-103.
    • (9) There was no significant difference in the MW parameters of the products from the (R)- and (S)-limonene. Consequently, the average of 4-8 values were used for the purpose of comparison. The results for the racemic limonene polymerizations are averages of 3-4 reactions. A full comparison between the results obtained in (R) and (S)-limonene will be presented in a forthcoming publication.
    • (10) The back-biting mechanism leading to termination only becomes significant above 70 °C. A full discussion of reactions conducted at temperatures below 70 °C will be presented in a forthcoming publication.
    • (11) No incorporation of the solvent into the polymer chain or effect on stereoregularity was observed by spectroscopic analysis of the PMPS. The chemical structures and tacticities of the polymers were identical to that observed for previous reported samples of PMPS.
    • (12) The % Lp, Ip, and Hp were consistently defined and analysed as MWs <1000 ) Lp, between 1000-10 000 ) Ip and >10 000 ) Hp.
    • (13) For clarity, error bars were omitted from Figure 3. See supporting information for comparative plots of Ip and Hp with temperature showing the results of error calculations.
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