Structural Confirmation of Exo-Olefin-Coupled Polyisobutylene Via Model Compound Synthesis and Characterization
Polymers and High Performance Materials
We report the synthesis and characterization of a model compound representing exo-olefin coupled polyisobutylene (PIB). Under certain conditions during the in situ quenching of quasiliving PIB with hindered bases to yield exo-olefin-terminated PIB, remaining PIB carbocations can undergo addition to exo-olefin PIB to yield coupled PIB with a molecular weight approximately double that of the primary chains. Characterization of the signals that arise in H-1-NMR from the presence of coupled product has not yet been properly performed; the accurate chemical shifts of these products, specifically the exo-olefin product, have been in debate recently. Therefore, we carried out the synthesis of a model compound which mimics the exo-olefin coupled product, and through variations in the synthetic method were able to produce a range of exo- and endo-olefin coupled product mixtures. The model compounds have been fully characterized using NMR techniques, and we herein conclusively report the proton shift (for 500MHz H-1-NMR in CDCl3) of 4.82 ppm for the exo-coupled product and that of 5.11 ppm for the endo-coupled product.
Journal of Macromolecular Science Part A-Pure and Applied Chemistry
Kemp, L. K.,
Poelma, J. E.,
Cooper, T. R.,
Storey, R. F.
(2008). Structural Confirmation of Exo-Olefin-Coupled Polyisobutylene Via Model Compound Synthesis and Characterization. Journal of Macromolecular Science Part A-Pure and Applied Chemistry, 45(2), 137-143.
Available at: http://aquila.usm.edu/fac_pubs/1694