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

64 B. Charleux, R. Faust
di- and trifunctional macromonomers have also been found to undergo chain
extension upon contact with proteinaceous materials such as human blood and
egg yolk.
Vinyl ether terminated PIBs with different endgroup structures (I and II in
Scheme 16) have been synthesized by Nemes et al. [108]. Scheme 16 summarizes
the key transformation steps.
In the first case PIB-Cl was dehydrochlorinated and metallated in a one pot
procedure. This was followed by coupling of the resulting PIB anion with CEVE.
In the second process, phenol was alkylated with PIB-Cl followed by a reaction
with CEVE. The value of F n determined by 1 H NMR spectroscopy indicated close
to quantitative functionalization. Copolymerization of the macromonomers has
not been reported.
Table 5 summarizes the work on the synthesis of macromonomers by cationic
polymerization.
3.3.2
Cationic Polymerization of Macromonomers
Generally, macromonomers are (co)polymerized by free-radical processes owing
to convenient experimental conditions, availability of a large number of
comonomers, and insensitivity of most chemical functions to the polymerization
conditions. Nevertheless, some macromonomers with a suitable end group
have been (co)polymerized by cationic polymerization. Provided that living cationic
polymerization conditions are applied, well-defined graft homopolymers
or copolymers can be prepared with a predetermined and uniform number of
branches.
3.3.2.1
Vinyl Ether Polymerizable Group
Macromonomers bearing a vinyl ether end group can be cationically polymerized.
This is the case for poly(vinyl ether) macromonomers prepared by living
cationic polymerization where the vinyl ether end group was introduced by endcapping
with the sodium salt of VOEM (see Sect. 3.3.1.2). For instance poly(IBVE)
and poly(BzOVE) macromonomers with homopolymer chain [89] and
poly(AcOVE-b-IBVE) with block copolymer chain of various length and composition
[90] were prepared by this technique. Preliminary studies showed that the
first two homopolymer macromonomers underwent quantitative cationic
homopolymerization and copolymerization with IBVE using HI/I 2 as an initiating
system in CH 2Cl 2 at –15 °C. A more comprehensive study was performed
with the block copolymer macromonomer. Living cationic polymerization was
carried out using the HI/ZnI 2 initiating system in toluene at –15 °C. The influence
of steric effect on conversion was examined by varying the total length of
the macromonomers at a constant AcOVE/IBVE molar ratio. It was shown that
the shorter the chain, the higher the polymer yield. Influence of the composition