Abstract:  Addition of a dialkyl ether, e.g., diisopropyl ether (DIPE) or di-sec-butylether (DSBE), to a TiCl4-co-initiated, living carbocationic polymerization of isobutylene (IB) results in capping of the chain ends with PIB diisopropyl oxonium cations, as evidenced by cessation of polymerization. Structure of PIB diisopropyl oxonium cations was determined using low temperature 500 MHz 1H NMR, by introducing diisopropyl ether to a mixture of TiCl4 and 2-chloro-2,4,4-trimethylpentane (TMPCl), a model for the PIB chain end, at -70�C in CS2/CD2Cl2 (50/50, v/v). One-pot, two-step quantitative synthesis of mono- and telechelic (difunctional) exo-olefin-terminated polyisobutylene (PIB) was achieved by quenching living PIB with DIPE, followed by termination with methanol at -60�C. TMPCl and 1,3-bis(1-chloro-1-methylethyl)-5-tert-butylbenzene (bDCC) were used as mono- and difunctional initiators respectively for IB polymerization. 1H NMR spectroscopy was used characterize the end-group composition of PIBs. Percent formation of exo-olefin was directly related to the steric bulk of the ether, i.e., sec-butyl (100%) � isopropyl (100%) > n-alkyl (68.5-81.5%). For [DIPE]/[CE] = 3, quantitative mono- and telechelic (difunctional) exo-olefin-terminated PIB was observed at [CE] = 0.1 M, for reaction volumes about 1 dL. 

Quantitative synthesis of <i>exo</i>-olefin-terminated polyisobutylene by ether quenching of living polyisobutylene

245th National Meeting (2013)

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Quantitative synthesis of exo-olefin-terminated polyisobutylene by ether quenching of living polyisobutylene