Star macromonomer approach

Scheme 27.2 The macromonomer approach" to synthesizing star-like polymers.

Fig. 22 Synthesis of peptide star-shaped polymers by the macromonomer approach Stages are synthesis of PBLG macromonomer with styrene end groups radical polymerization (SERF or RAFT) in the presence of DVB by crosslinking of block copolymers and deprotection of PBLG shell [132]...

Statistical, gradient, and block copolymers as well as other polymer architectures (graft, star, comb, hyperbranched) can be synthesized by NMP following the approaches described for ATRP (Secs. 3-15b-4, 3-15b-5) [Hawker et al., 2001]. Block copolymers can be synthesized via NMP using the one-pot sequential or isolated macromonomer methods. The order of addition of monomer is often important, such as styrene first for styrene-isoprene, acrylate first for acrylate-styrene and acrylate-isoprene [Benoit et al., 2000a,b Tang et al., 2003]. Different methods are available to produce block copolymers in which the two blocks are formed by different polymerization mechanisms ... 

Individual methods have also been devised for the preparation of miktoarm stars. One of these approaches involves the preparation of macromonomers possessing either central or end vinyl groups which can be used to produce miktoarm stars either by copolymerization of the double bonds or by reacting the double bonds with living polymer chains, thus creating active centers able to initiate the polymerization of another monomer. All these methods are limited to specific synthetic problems and cannot be used for the preparation of a wide range of different structures. 

So far, there have been only few reports about the synthesis of amphipolar polymer brushes, i.e. with amphiphilic block copolymer side chains. Gna-nou et al. [115] first reported the ROMP of norbornenoyl-endfunctionalized polystyrene-f -poly(ethylene oxide) macromonomers. Due to the low degree of polymerization, the polymacromonomer adopted a star-like rather than a cylindrical shape. Schmidt et al. [123] synthesized amphipolar cylindrical brushes with poly(2-vinylpyridine)-block-polystyrene side chains via radical polymerization of the corresponding block macromonomer. A similar polymer brush with poly(a-methylstyrene)-Wocfc-poly(2-vinylpyridine) side chains was also synthesized by Ishizu et al. via radical polymerization [124]. Using the grafting from approach, Muller et al. [121, 125] synthesized... 

An alternative approach to synthesis of star-shaped polymers or nanoparticles is the use of macromonomers. The Heise group prepared PBLG macromonomers with a styrene endgroup by NCA polymerization initiated with 4-vinylbenzylamine. The macromonomers were then copolymerized with divinylbenzene by free-radical or RAFT polymerization (see Fig. 22). Finally, the peptide block was deprotected to give PGA blocks and resulted in pH-responsive water-soluble nanoparticles [132]. 

Figure 11 Star polymers synthesized by a grafting-to approach using divinyl acrylic monomers and CCTP macromonomers.

The second approach is the copolymerization of a maao-monomer with a divinyl monomer in the presence of a low MW initiator.The sequential addition of initiator and CTOss-linker to the reaction increases the number of macromonomer units incorporated into each star. ... 

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