Synthesis of Triphenylsilylmethyl and Triphenylmethyl-Telechelic Polyisobutylene: An Approach to the Synthesis of Multi-Ion Telechelic Ionomers

Triphenylsilyl- and triphenylmethyl-telechelic polyisobutylene (PIB) were prepared by lithiation of three-arm star PIBs carrying either olefinic or tert-alkyl chloride end groups, followed by reaction with triphenylsilyl chloride or triphenylcarbenium ion, respectively. Since the lithiated intermediate is a substituted allylic carbanion, the chain end also possesses a double bond which is located beta-gamma relative to the silyl or triphenylmethyl group. The phenyl groups were incorporated into the polymers to provide extra sites for sulfonation, in addition to the double bond, to enable the synthesis of multi-ion telechelic ionomers. H-1- and C-13-NMR spectroscopy showed that triphenylsilylation and triphenylmethylation were essentially quantitative when applied under the prescribed conditions to either the model compound, 2,4,4-trimethyl-1-pentene, or to the telechelic PIBs. It was observed that exhaustive sulfonation of these materials using acetyl sulfate or chlorosulfonic acid yielded only about 50% sulfonation of the available sites. This suggests that sulfonation of closely adjacent, multiple sites within the same molecule fails due to deactivation of the remaining sites after one or perhaps two sulfonations. However, the triphenylsilyl- and triphenyl-methyl-telechelic PIBs represent novel prepolymers which can perhaps be derivatized by some method other than sulfonation, and the general concept for producing telechelic ionomer precursors with multiple sulfonation sites may prove successful with other moieties containing spacer groups between sites