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

Synthesis of Branched Polymers by Cationic Polymerization 65
was also studied and it appeared that a larger amount of AcOVE was responsible
for retardation of the polymerization because the ester group could complex the
Lewis acid and reduce its effective concentration. Finally, the best conditions
were found for a macromonomer with 5 AcOVE units and 10 IBVE units (M n =
2600 g mol –1 with M w /M n =1.13 and F n =1.10). Homopolymerisation was carried
out in toluene at –15 °C and 85% conversion were reached in 3 h to lead to a
higher MW polymer with narrow MWD (M w =15,000 g mol –1 as determined by
light scattering after fractionation and M w /M n =1.16 as determined by SEC). The
calculated DP n was 6.3 which was very close to the theoretical value and indicated
that living polymerization conditions were fulfilled leading to a well-defined
star-like block copolymer with the predetermined and uniform number of
branches. The pendant ester groups of AcOVE were hydrolyzed to their alcoholic
counterpart to give the amphiphilic graft copolymer, the solubility properties of
which were compared with the corresponding linear and star block copolymers.
Some previously reported sequence-regulated macromonomers [97] were
also homopolymerized using non-living (BF 3OEt 2 as an initiator in toluene at
–15 °C) and living conditions (HI/ZnI 2 as an initiator in toluene at –15 °C). In
both cases, nearly quantitative conversion of the two macromonomers was
reached, indicating their ability to undergo cationic polymerization. However,
in the first case, a considerable amount of dimer was recovered whereas, under
living conditions, the resulting polymer had an average degree of polymerization
of 9.4, very close to the theoretical value, with narrow MWD
(M w/M n