Self-condensing vinyl polymerizations

With appropriate choice of reaction conditions, hyperbranched polymers can be formed by sclf-condcnsing vinyl polymerization of monomers that additionally contain the appropriate initiator (NMP, ATRP), when the compounds are called inimers, or RAFT agent functionality. Monomers used in this process include 340,716 341717 and 34204 (for NMP), 108714,714 and 344 and related monomers720 723 (for ATRP) and 343408 (for RAFT). Careful control of reaction conditions is required to avoid network formation. 

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Table 2. Molecular parameters of polymers obtained by self-condensing vinyl polymerization and copolymerization...

Figure 8.4 Self-condensing vinyl polymerization of 3-(1-chloroethyl)-ethenyl-benzene requires an external activator, in this case the activator is SnCI4 [19]...

Figure 8.5 Schematic representation of the self-condensing vinyl polymerization of an AB -monomerto give a hyperbranched vinyl polymer [19]...

The second generation of hyperbranched polymers was introduced a few years ago when Frechet et al. reported the use of self-condensing vinyl polymerization to prepare hyperbranched polymers by carbocationic systems (Fig. 3) [46]. Similar procedures but adapted for radical polymerization were shortly thereafter demonstrated by Hawker et al. [47] and Matyjaszewski et al. [48]. 

Fig. 3. Schematic description of self-condensing vinyl polymerization used for the synthesis of of hyperbranched polymers based on vinyl monomers as presented by Frechet [52] -(represents a reactive site which can initiate polymerization)...

Hyperbranched polymers can be synthesized in several different ways, the most commonly used being classical condensation reactions. These reactions are made either in bulk or in solution where the A,jB monomers are condensed by themselves or in combination with a By core monomer. The use of a By core monomer improves the control over the molecular weight and dispersity of the hyperbranched polymer. Hyperbranched polymers can also be synthesized by self-condensing vinyl polymerization using vinyl-functional monomers. The introduction of this approach has greatly increased the number of possible monomers that can be used for this type of polymer. 

A wide variety of hyperbranched polymers have been described in the literature. Initially, these were mainly condensation polymers such as polyesters and polyethers since the required monomers were the most readily available. A number of hyperbranched polymers based on vinyl monomers have been described lately after the introduction of self-condensing vinyl polymerization. One structural variation which has been widely employed for hyperbranched... 

Fig. 9.35 Schematic illustration of the self-condensing vinyl polymerization ATRSIP on planar silica substrates resulting in hyper-branched surface-bonded polymer layers.

Self-condensing vinyl polymerization was first demonstrated with 3-(l -chlo-roethyl)-ethenylbenzene as an AB type monomer. The cationic polymerization was induced by SnCl4 in CH2C12 at -15 or -20 °C in the presence of tetrabutylam-moniumbromide (Scheme 17). 

The self-condensing vinyl polymerization, which was initially developed for living cationic polymerization,442 is also applicable for metal-catalyzed living radical polymerizations. 

The self-condensing copper-catalyzed polymerization of macromonomer of poly(tBA) with a reactive C—Br bond (H-6) affords hyperbranched or highly branched poly(tBA).447 Copolymerization of H-1 and TV-cyclohexylmaleimide induced alternating and self-condensing vinyl polymerization.448 The residual C—Cl bond was further employed for the copper-catalyzed radical homopolymerization of styrene to give star polymers with hyperbranched structures. Hyperbranched polymers of H-1 further serve as a complex multifunctionalized macroinitiator for the copper-catalyzed polymerization of a functional monomer with polar chromophores to yield possible second-order nonlinear optical materials.325... 

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