Copolymers and Other Architectures

We are currently exploring new routes to the synthesis of ionomers with controlled architecture, i.e. with control over the amount and location of ionic groups in the polymer backbone. One of our main interests is the synthesis of ion containing block copolymers. The applicability of anionic polymerization in the synthesis of block copolymers and other well defined model systems is well documented (22-24) Not as well appreciated, however, is the blocky nature that certain emulsion copolymerizations may provide. Thus, we have utilized both anionic and free radical emulsion polymerization in the preparation of model ionomers of controlled architecture. In this paper, the synthesis and characteristics of sulfonated and carboxylated block ionomers by both free radical emulsion and anionic polymerization followed by hydrolysis will be discussed. 

Chong, Y.K., Le, T.P.T., Moad, G., et al., 1999. A more versatile route to block copolymers and other polymars of complex architecture by living radical polymerization the RAFT process. Macromolecules 32 (6), 2071—2074. 

Initially, a major drawback of the transition-metal-mediated NCA poljuner-ization, as it is outlined in Fig. 3, was the lack of control over the chain end fimctionality of the polypeptide chains. This is in great contrast to, eg, primary amine initiated NCA poljunerizations, which are widely explored for the preparation of synthetic-peptide block copolymers and other peptide-hybrid architectures. This limitation could be overcome by the direct synthesis of the amido amidate metallacycle propagating species (eq. 4) (42). 

Living polymerization was discovered in anionic system by Szwarc (see p. 476) in 1950, which, as we shall see in Chapter 8, offers many bene ts including the ability to control molecular weight and polydispersity and to prepare block copolymers and other polymers of complex architecture. Many attempts have then been made to develop a living polymerization process with free-radical mechanism so that it could combine the virtues of living polymerization with versatility and convenience of free-radical polymerization. Considering the enormous importance and application potential of living/controlled radical polymerization techniques, these will be considered in detail in another chapter (Chapter 11) with a state-of-the art discussion on the subject. 

Although anionic polymerisation remains an important technique today for the preparation of block copolymers and other controlled polymer architecture, recent developments in controlled free-radical polymerisation has presented an alternative approach which may complement this methodology. 

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