Homopolymerization metal containing monomers

I, vinylruthenocene, 66, vinylosmocene, and the T)5-(vinylcyclopentadienyl)metal carbonyl monomers in radical-initiated polymerizations summarized in Scheme 1.1 no longer exists for anionically initiated addition polymerizations. Styrene is readily initiated by such anionic species as BuLi and Na1 Naphth. Living anionic styrene homopolymerizations and block copolymerizations have been extensively commercialized for many years (e.g., Kraton thermoplastic elastomers). However, the exceptionally electron-rich vinyl metal-containing monomers 1, 8-18, 24-30, and 66 were never successfully initiated by anionic systems in our laboratory despite many attempts. In these systems, the a-carbocations are very stable, but the a-carbanions are quite unstable. Thus, the addition of an anion to tbe vinyl function of these monomers is unfavorable. 

Different valence states are also a fairly widespread type of unit variability. By analogy with macromolecular complexes (Section II), it may be expected that homopolymerization and copolymerization of metal-containing monomers would prevent or retard redox processes involving participation of metal ions. Experimental data confirm the fact that a polymeric matrix stabilizes complexes of metals in low oxidation states (e.g., Pd" ). Moreover, the stability of the Cu+ state during polymerization (including thermal polymerization) of copper acrylate controls the use of this method for the preparation of coordination compounds of Cu". The polymeric framework plays a stabilizing role, whereas the metal ions that are localized on the surface layer are oxidized to Cu +. However, polymerization of monomers that contain metal ions in high oxidation states is often accompanied by their reduction Fe + ->Fe +, and Mo + ->Mo" (scheme 14). For example, polymerization of Cu " and Fe + acrylates may be accompanied by intramolecular chain termination. This may be attributed to the relatively low standard reduction potentials of these metal ions (7io(Cu + Cu+) = 0.15, o(Fe ->Fe ) = 0.77 V). 

Vinylferrocene is one of the few transition-metal-containing monomers that will both homopolymerize and copolymerize with other vinyl monomers in the presence of free-radical initiators. 

Cqpolymerization of MCM with traditional monomers is the main technique of metal insertion into a polymer chain, and it is more widely used than their homopolymerization. However, ocpolymerization laws in such systems are difficult to analyze because of their raultiparameter dependence of the kinetics and copolymerization characteristics on the process, parameters such as pH, solvent nature and even concentration ratio (30). The metal-containing giroup in MCM is, as a rule, an electron-donor substituent (scheme Q-e). The copolymerization yields complexes of different comonomers, effecting the polymer composition and structure. In our view, the most remarkable one is cqpolymerization of transition metal diacrylates with MMA, styrene, etc. (37), as well as vinylpyridine and vinylimidazole MX complexes and formation of ternary copolymers of the following composition (38) ... 

The attachment of cymantrene groups to polymers has attracted interest for other reasons. Studies have shown, for example, that adherent, abrasion-resistant coatings are formed on metals when thin films of the Mn-containing polymer are subjected to irradiation with UV light. The polymerization of styrene tricarbonylchromium 47 has also been studied.This species is available from the reaction of styrene with Cr(CO)3(NH3)3. Although the Cr monomer 47 resisted attempts at homopolymerization, co-polymerizations with styrene, methyl acrylate, as well as with 41 to yield bimetallic polymers 48 were possible (Equation (17)). In addition, co-polymerization with vinyl-ferrocene afforded co-polymers of low molecular weight (Mn = ca. 4,000). A variety of other organometallic vinyl momomers 49 has been successfully polymerized to yield polymers 50 that contain pendant Gr, W, and Ir carbonyl moieties (Equation (18)). ... 

As far as PP with oxidizable substituents is concerned, polymerization of monomers in this class is complicated by the fact that the substituent can be oxidized at a less positive potential than that necessary to polymerize the pyrrole ring. Ferrocene-containing pyrroles have been prepared, but homopolymerization resulted in uneven deposits [260,261]. Pyrroles with attached metal complexes, such as pyridine [262,263], porphyrin [264-266], and cyclam [267] complexes, have been studied. 

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