Isobutene polymerization initiated by [CP*TiMe2]+ in the presence of a series of novel, weakly coordinating counteranions
Article first published online: 21 AUG 2002
Copyright © 2002 Wiley Periodicals, Inc.
Journal of Polymer Science Part A: Polymer Chemistry
Volume 40, Issue 19, pages 3302–3311, 1 October 2002
How to Cite
Kumar, K. R., Hall, C., Penciu, A., Drewitt, M. J., McInenly, P. J. and Baird, M. C. (2002), Isobutene polymerization initiated by [CP*TiMe2]+ in the presence of a series of novel, weakly coordinating counteranions. J. Polym. Sci. A Polym. Chem., 40: 3302–3311. doi: 10.1002/pola.10416
- Issue published online: 21 AUG 2002
- Article first published online: 21 AUG 2002
- Manuscript Accepted: 8 JUL 2002
- Manuscript Received: 29 MAR 2002
- Queen's University
- Natural Sciences and Engineering Research Council
- Bayer, Inc.
- cationic polymerization;
The highly electrophilic borane B(C6F5)3 reacts with n-octadecanol (n-C18H37OH) and n-octadecanethiol (n-C18H37SH) to form the 1:1 adducts (n-C18H37EH)B(C6F5)3 (E = O or S). The latter are acidic and react with Cp*TiMe3 in methylene chloride and toluene to give methane and the complexes [Cp*TiMe2][(n-C18H37E)B(C6F5)3], which are very good initiators for the carbocationic polymerization of isobutene (IB) from −40 to −20 °C. High conversions to high molecular weight polyisobutene (PIB) in methylene chloride and moderate conversions to high molecular weight PIB in toluene are observed and are consistent with the anions [(n-C18H37E)B(C6F5)3]− being very weakly coordinating. Although polymerization in methylene chloride is too rapid for the temperature to be controlled, polymerization in toluene is slower, and the temperatures can be controlled so that Arrhenius-type plots of the logarithm of the number-average molecular weight versus T−1 = 1/T may be obtained. Activation energies for the degree of polymerization in these polymerization reactions and similar polymerizations carried out with n-C18H37EH:borane ratios of 1:2 and with the activators [Ph3C][B(C6F5)4] and Al(C6F5)3 range from −11 to −27 kJ mol−1, values comparable to those for most conventional IB polymerization initiators. However, the values of the weight-average and number-average molecular weights are unusually high for the temperatures used, and this is consistent with current theories of the role of weakly coordinating anions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3302–3311, 2002