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

56 B. Charleux, R. Faust
macromonomer [95, 96] was obtained with the following monomers sequence:
n-butyl vinyl ether (BVE), VOEM, BzOVE, and 2-(vinyloxy)ethyl methacrylate,
this latter monomer being used to incorporate a terminal methacrylate. The
macromonomer was purified from by-products by preparative size exclusion
chromatography. The second example was a heterodimer quenched with the
malonate anion 36 [97]. It was prepared by a three step technique: quantitative
addition of HI to the first vinyl ether, addition of one equivalent of a second
monomer (preferably less reactive than the first one) in the presence of ZnI 2 , and
finally quenching with 36 which allowed introduction of the polymerizable vinyl
ether end group. Two macromonomers were synthesized by this method with
the respective following sequence: BVE/BzOVE and 2-ethylhexyl vinyl
ether/CEVE.
3.3.1.2.2
Poly(p-alkoxystyrenes)
Owing to the lower stability of growing p-alkoxystyrene cations and to the possibility
of several side-reactions, some end-capping agents which were successfully
used for poly(vinyl ether)s such as sodiomalonic ester and tert-butyl alcohol,
did not give end-functionalization with poly(p-alkoxystyrene) cations. In
contrast, primary and secondary alcohols underwent quantitative reactions to
give stable alkoxy functional groups. Thus, 2-hydroxyethyl methacrylate and
acrylate were used to introduce a polymerizable group at the w end [98, 99]. Living
cationic polymerizations of p-MOS and tBOS were carried out at –15 °C in
toluene using HI/ZnI 2 as an initiating system. When the monomer conversion
was complete, a large excess of the quencher was added, resulting in a quantitative
functionalization. The polymerization was shown to be living and well-defined
macromonomers with narrow MWD and one polymerizable acrylate or
methacrylate functional group per chain were obtained. Heterotelechelic poly(p-MOS)s
were also prepared by the combination of the functional initiator
method and the functional end-capping method. This allowed the synthesis of a
poly(p-MOS) macromonomer with one malonate diester at the a end and one
methacrylate group at the w end.
3.3.1.2.3
Poly(styrene)
The living cationic polymerization of styrene could be achieved using 1-phenylethyl
chloride as an initiator in the presence of SnCl 4 and n-Bu 4 NCl. However,
in contrast to vinyl ethers and p-alkoxystyrenes, quenching with usual bases
such as methanol, sodium methoxide, benzylamine, or diethyl sodiomalonate
led to the terminal chloride instead of the specific end group. This was explained
by the very low concentration of cationic species in comparison with the dormant
C-Cl end group and also by the low reactivity of this C-Cl functional group
in substitution reactions. This was overcome using organosilicon compounds