Cobalt-mediated radical polymerization

The synthesis of a well defined poly(vinyl alcohol)-b-poly(aciylic acid) (PVA-PAA) DHBC has been recently reported in the literature [32] by a two step synthetic scheme. First the synthesis of a poly(acrylonitrile) (PAN) block was realized via cobalt-mediated radical polymerization, using a poly(vinyl acetate) (PVAc) macroinitiator, followed by hydrolysis of both blocks. The polymerization was performed in DMF, a very good solvent for PAN, and at low temperature, where block copolymers with low polydispersity were obtained. The polymerization procedure led to well defined macromolecules with relatively high molecular weights. The obtained copolymers were transformed to the desired DHBCs by hydrolysis, using large excess of potassium hydroxide in a water/ethanol mixture. The successful completion of the hydrolysis reaction was monitored by NMR and IR spectroscopy. An additional macroscopical indication of the DHBC formation was the aqueous solubility of the reaction product. 

DEB 05] Debuigne A., Caille J.-R., Jerome R., Highly efficient cobalt-mediated radical polymerization of vinyl acetate , Angewandte Chemie International Edition, vol. 44, pp. 1101-1104, 2005. 

DEC 98] Decker C., Highly efficient cobalt-mediated radical polymerization of... 

More monomers are mentioned in patent literature but details of the reaction conditions are discrete. One such example is the CCTP of a hydrophilic acrylic macromonomer. Sodium acrylate and ammonium acrylate homopolymers are mentioned and most likely to be examples of cobalt-mediated radical polymerization (CMRP) rather than of CCTP. ... 

Figure 9 Cobalt(ll) bis(p-diketonates) used in cobalt-mediated radical polymerization.

Figure 36 General strategy for polymer release and regeneration of the Co" complex in cobalt-mediated radical polymerization of VAc (the nature of the PVAc-Co" dormant species is more likely a ligand adduct, like IX, or a chelated species, like X, depending on conditions, see Figure 10 and related discussion in Section 3.11.5.5).

Besides the most common CRP methods used to control the radical polymerization of vinylic monomers, other techniques have been developed over the time, and have been tested in miniemulsion or emulsion polymerization as well. These methods are described in the corresponding chapters of this comprehensive. They are iodine transfer polymerization (ITP and the reverse method, RITP), organotelluriirm-mediated CRP (TeRP), and cobalt-mediated radical polymerization (CoMRP). 

Four-arm stars [poly(vinyl acetate) ]4C6o have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc) followed by addition of the PVAc-Co(acetylacetonate)2 chains to the fullerene [30]. The photoactive water-soluble [poly(vinyl alcohol) hCgo was then obtained by hydrolysis of the PVAc arms. Because... 

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