Macromonomers, poly

Scheme 8. Synthesis of a poly(vinylpyridin)-poly(macromonomer). Reproduced with the permission of Wiley VCH from reference 34...

Poly(macromonomers) with moderately long side chains attached to every few (second) atom along the backbone are very densely branched polymers. When the degree of polymerization of the backbone is low then the poly(macromon-mers) tend to resemble star polymers [39, 40]. When the degree of polymerization is very high the poly(macromonomer) acquires a cylindrical conformation (bottlebrush), due to the stretching and linearization of the backbone [40]. 

Keywords. Poly(macromonomers), Graft copolymers, Comb, Star, Brush, Polymeric microspheres... 

Fig. 1 a—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... 

So far, a great number of well-defined macromonomers as branch candidates have been prepared as will be described in Sect. 3. Then a problem is how to control their polymerization and copolymerization, that is how to design the backbone length, the backbone/branch composition, and their distribution. This will be discussed in Sect. 4. In brief, radical homopolymerization and copolymerization of macromonomers to poly(macromonomers) and statistical graft copolymers, respectively, have been fairly well understood in comparison with those of conventional monomers. However, a more precise control over the backbone length and distribution by, e.g., a living (co)polymerization is still an unsolved challenge. 

Fig. 2a,b. Models of a propagation reaction of a poly(macromonomer) radical with a macromonomer b bimolecular termination between poly(macromonomer) radicals... 

Polymacromonomers can be geometrically classified into two types of regular branched forms, i.e., stars and combs, depending on the degree of polymerization of the backbone and side chains. The poly(macromonomers) are probably... 

The g factors of some star-shaped polymacromonomers with relatively limited number of arms have been investigated and compared with the theory mentioned above. Tsukahara et al. [61] estimated the g factors of PSt polymacromonomers from 24 by SEC-LALLS measurement and compared with Eqs. (6) and (8). The results suggest that these poly(macromonomers) behave like star polymer. The experimental value of g is larger than the theoretical one based on Eq. (6) in agreement with results of studies on model star polymers [62]. 

Fig. 4. Double logarithmic plots of Z1/2 vs Mw of poly(macromonomer) of 26 (m=4, n= 50) in 0.05 N NaCl H20 at 25 °C. Open symbols (o) are experimental results. The closed symbols (1) are calculated values by Eqs. (5) and (6). The thick solid line is theoretical, calculated from Eqs. (11) and (14-17) for the perturbed KP chain with q=17 nm, ML=1.03X104nm 1, and B=5.78 nm the dashed line is theoretical, calculated for the unperturbed KP chain (B=0)...

Characterization of the poly(macromonomers) prepared by homopolymerization has proved that they provide a useful probe for discussing the structural characteristics of the star and brush polymers. Graft copolymers have been and will be a most important area of application of the macromonomer technique since a variety of multi-phased and microphase-separated systems can easily be designed just by an appropriate combination of a macromonomer and a conventional monomer. In general, however, characterization of their absolute MW, branch/backbone composition as well as their distributions remain to be studied in more detail. 

Furthermore, the group of Deimede [338-340] performed the synthesis of a-dicarboxy end-functionalized PS macromonomers by using ATRP (Scheme 72). Further polycondensation with dihydroxy end functionalized polyethylene oxide) led to alternating branched PS/poly(ethylene oxide) poly(macromonomers) (Scheme 72). These novel amphiphilic compounds afforded the formation of stable micelles, especially in THF or dioxane. 

Scheme 72 Synthesis of alternating branched polystyrene/poly(ethylene oxide) poly-(macromonomers)...

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