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

134 K. Ito, S. Kawaguchi
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Survey of Macromonomer Techniques
A macromonomer is usually defined as a polymeric or an oligomeric monomer
with a polymerizable or copolymerizable functional group at one end. They afford
a comb-shaped polymer with regularly and densely attached branches by
homopolymerization, and a graft copolymer with randomly and loosely distributed
branches by copolymerization with a conventional, low molecular weight
(MW) comonomer, as illustrated in Fig. 1a,b, respectively. A formally combshaped
poly(macromonomer) may actually be forced to take a conformation
that looks like a star as in Fig. 1c or a brush as in Fig. 1e, depending on the relative
lengths of the macromonomer branch vs the poly(macromonomer) backbone.
A graft copolymer with a relatively short backbone as compared to the
branches may also look like a star as in Fig. 1d in a solvent which is selective for
the branches, while that with a long backbone with few but long branches may
take a flower-like conformation as in Fig. 1f with some of their backbone segments
looped outside in a selective solvent for the backbone. These isolated conformations
favored in dilute solutions are expected to coalesce to some organ-
Fig. 1a–f. Various branched architectures obtained by the macromonomer technique: a,b
comb-like; c,d star-like; e brush; f flower-like. a c, and e are poly(macromonomers) obtained
by homopolymerization, while b, d, and f are graft copolymers obtained by copolymerization