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

136 K. Ito, S. Kawaguchi
mers are reactive emulsifiers or dispersants in emulsion or dispersion systems,
respectively. Since the macromonomers are already polymers, they serve as effective
steric stabilizers of the resulting microspheres. They are surface grafts
after copolymerization with the substrate comonomer. A number of hydrophilic
or polar macromonomers have been designed for aqueous emulsion
or alcoholic dispersion systems. They are the counterpart of the nonpolar macromonomers
which were indeed the first “macromonomers” developed for the
well-known nonaqueous (petroleum) dispersion polymerization (NAD) by ICI
[7].
3
Syntheses of Macromonomers
Macromonomers are synthesized by introducing an appropriate (co)polymerizable
end-group, generally by one of the following methods: (a) end-capping
of a living polymer (termination method), (b) initiation of living polymerization
(initiation method), (c) transformation of any functional end-group, and
(d) polyaddition. Methods (a) and (b) are simple and usually afford most welldefined
macromonomers of a controlled degree of polymerization with a narrow
MW distribution, but depend on proper combination of any living polymerization
with an effective terminator or initiator carrying a polymerizing
group or its protected one. Method (c) utilizes any end-functionalized polymers
such as those obtained from chain-transfer-controlled radical polymerization
and polycondensation. Method (d) involves the polyaddition reactions
between vinyl and silane groups (hydrosilylation), for an example. Since more
than one hundred macromonomers have been reviewed previously [1], including
polyolefins, polystyrenes, polydienes, polyvinylpyridines, poly(meth)acrylates
and their derivatives, poly(vinyl ethers), poly(vinyl acetate) and derivatives,
halogenated vinyl polymers, poly(alkylene oxides), poly(dimethylsiloxanes),
poly(tetrahydrofuran) and polyacetals, polyoxazolines and poly(ethyleneimines),
polylactones and polylactide, polylactams and poly(amino acids),
and macromonomers prepared by polycondensation and polyaddition,
only very recent developments will be described here in a way to supplement
them.
3.1
Polyolefins
End-functionalized polyethylene (PE) [8, 9], polypropylene (PP) [10], and
polyisobutylene (PIB) [11] have been transformed to their corresponding macromonomers
carrying (meth)acrylate, oxazoline, and methacrylate end groups,
1, 2, and 3, respectively. Polybutadienyl lithium was terminated with chlorodimethylsilane,
followed by hydrogenation to saturated polyolefin (PHBd)
[12]. Hydrosilylation of the end silane with allyl glycidyl ether afforded an epox-