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

Synthesis of Branched Polymers by Cationic Polymerization 41
The known methods to prepare star polymers and copolymers via living cationic
polymerization with multifunctional coupling agents are summarized in
Table 3.
3
Graft (co)Polymers
Graft (co)polymers are polymers with a linear backbone to which macromolecular
side chains are connected. They can be prepared by three different methods:
“grafting from”, “grafting onto”, and (co)polymerization of macromonomers.
3.1
“Grafting From” Technique
This technique is based on the use of a linear polymer with pendant functional
groups that can be activated to initiate the polymerization of a second monomer.
Based on this definition, the linear precursor polymer can be considered as a
multifunctional macromolecular initiator. The importance of the “grafting
from” technique by cationic polymerization of the second monomer increased
considerably with the advent of living cationic polymerization. The advantage is
the virtual absence of homopolymer formation via chain transfer to monomer.
3.1.1
Synthesis of the Backbone by Cationic Polymerization
3.1.1.1
Poly(vinyl ether) Backbone
Graft copolymers with poly(vinyl ether) backbone and poly(2-ethyloxazoline)
branches were reported [58] where the backbone, a random copolymer of poly(EVE)
and poly(CEVE), was prepared by conventional cationic polymerization
using aluminium hydrogen sulfate as an initiator in pentane at 0 °C. After
quenching the copolymer with methanol, quantitative polymerization of 2-ethyloxazoline
was performed using the pendant chloroethyl sites as initiators in the
presence of sodium iodide in chlorobenzene at 115 °C. The obtained graft copolymer
exhibited two glass transition temperatures indicating a phase separated
morphology.
3.1.1.2
Poly(isobutylene) Backbone
The simplest method to obtain PIB backbone with pendant functionalities able
to initiate polymerization of a second monomer is via copolymerization of IB
with a functional monomer such as bromomethylstyrene (BMS) or chlorometh-