142 Advances in Polymer Science Editorial Board: A. Abe. A.-C ...

Synthesis of Branched Polymers by Cationic Polymerization 21
achieve owing to the possibility of b-proton elimination and subsequent polymerization
of the new double bonds. The two-step end-capping of the polystyrene
stars with C 60 was also recently reported [25]. The first step was the introduction
of six azido end groups by reaction of the stars with TiCl 4 and Me 3 SiN 3 ; the reaction
was found to be quantitative according to 1 H NMR analysis. The second
step was performed by refluxing the star with an excess of C 60 in chlorobenzene;
1 H and 13 C NMR confirmed quantitative grafting.
2.2.1.4
Poly(isobutylene) n
Three arm star PIBs have been first synthesized by the inifer technique using the
tricumyl chloride (TCC, 14)/BCl 3 initiating system in CH 3 Cl at –70 °C [26].
(14) X=Cl
(15) X=OCH 3
(16) X=OCOCH 3
(17) X=OH
The inifer technique yields tert-chloro telechelic PIBs (Scheme 2) with M n s
determined by the [monomer]/[inifer] ratio. To prepare telechelic products,
chain transfer to monomer must be absent, and with BCl 3 as coinitiator this requirement
is fulfilled.
Characterization of the three arm star PIB involved a variety of spectroscopic
techniques, i.e., 1 H and 13 C NMR, IR, and UV, thermal dehydrochlorination, and
Scheme 2