Biomimetic processes II. Carbocationic polymerization of isopentenyl alcohol: A model for the synthesis of natural rubber?

Natural rubber (poly(1,4-cis-isoprene), NR), a polymer of considerable industrial importance due to its exceptional properties, is exclusively produced from the cultivation of Hevea brasiliensis. After numerous attempts by polymer chemists to try to synthesize polyisoprene with very similar structures, none have been produced that exhibit such excellent properties. In this paper we analyze a new bio-inspired route towards NR based on the carbocationic polymerization of isopentenyl pyrophosphate (IPP) (the natural monomer) and its derivatives. We report in an initial study, the carbocationic polymerization of isopentenyl alcohol (IPOH) under various polymerization conditions. It is shown that oligomers are produced via 1,2 addition and not via the expected 1,4 addition.