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

Poly(macromonomers), Homo- and Copolymerization 173
Fig. 9. Plots of mobile fraction(f M ) of surface anchored PEO chains against the estimated
mean separation D between PEO anchor points on the surface of the particles. The D values
were calculated from the particle size and number, assuming that all PEO chains were located
at the surface
below D=1.4 nm. The radius of gyration of the PEO chain coil in methanol is calculated
to be 1.6 nm, which corresponds to the D value at which the sharp increase
in f M occurs. This result may suggest that the onset of a pancake-to-brush
transition of grafted chains at the interface occurs when D» 1/2 , as was expected
from theory [130, 154, 155]. This kind of subject is of importance for a
better understanding of the true nature of the steric stabilization existing in
many dispersion systems. With these guidelines, the macromonomer technique
will be used extensively to construct model colloidal systems.
7
Conclusions and Future
A number of well-defined macromonomers differing in the types of the monomer
and the end functionality have been made available in these two decades.
Their polymerization and copolymerization have provided a relatively easy access
to a variety of branched polymers and copolymers, including comb-, star-,
brush-, and graft-structures. Progress will no doubt continue to disclose further
different types of macromonomers and branched polymers.
Radical homopolymerization and copolymerization of macromonomers are
fairly well understood and reveal their characteristic behaviors that have to be
compared with those of conventional monomers. A detailed mechanism of the
polymer-polymer reactions involved, however, appears still to be an issue. Ionic
or, desirably, living polymerization and copolymerization are still an important