Metal-containing monomers transition

The incorporation of metal ions into a polymer chain—directly or via ligands— offers imique materials with properties that differ significantly from those of conventional organic polymers. The different range of coordination munbers especially of transition metal ions can allow the preparation of polymers with imusual conformational, mechanical, and morphological characteristics. All above considered types of MMCs can be also obtained by polymerization and copolymerization of metal-containing monomers. ... 

ROMP copolymers have been functionalized in order to introduce photosensitive groups with a view to bringing new functionalities. Biological detection with signal amplification has been explored by Sleiman et al. [74] from ROMP copolymers incorporating luminescent and electrochemiluminescent transition-metal-containing monomers, biologically compatible monomers, macromonomers... 

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. 

Conjugated boron polymers containing platimnn or palladium atom in the main chain were also prepared by hydroboration polymerization between tetrayne/ metal complex monomers and tripylborane (scheme 16).30 From gel permeation chromatographic analysis [THF, polystyrene (PSt) standards], the number-average molecular weights of the polymers obtained were found to be 9000. The polymers were soluble in common organic solvents such as THF, chloroform, and benzene. The absorption peaks due to tt-tt transition were observed around 390 nm in the UV-vis spectra of these polymers. The fluorescence emission spectra exhibited intense peaks at 490 nm in chloroform. 

A major limitation of such Group IVB metallocene catalysts is that they are air- and moisture-sensitive and not tolerant to heteroatom-containing monomers. In the case of heteroatom-containing monomers the unbonded electron pairs on the heteroatom, such as oxygen, preferentially coordinate to the Lewis acid metal center in place of the carbon-carbon double bond. Some so-called middle and late transition metal organometallics are more tolerant to the presence of such heteroatoms and can be used as effective cocatalysts. These include some palladium, iron, cobalt, and nickel initiators. 

Both typical and exceptional examples of the polymerization of a vinyl monomer containing a transition-metal ion are provided by the radical polymerization of vinylferrocene31. Vinylferrocene and its derivatives are polymerized by a radical or a cationic initiator to form a polymer of high molecular weight. The high polymeriz-ability is based on the property that the ferrocene compounds are extraordinarily stable against chemical reactions. 

Note that the transformation of metal carbene vice versa, during polymerisation occurs as in the case of cycloalk-ene ring-opening metathesis polymerisation. Considering the mechanism of metathesis polymerisation of acetylenic monomers, it is worth noting that catalysts containing a transition metal carbyne bond (Mt=C) can induce polymerisation only when this bond is transformed into the respective metal carbene bond (Mt=C) [39],... 

The two-component catalytic systems used for olefin polymerization (Ziegler-Natta catalysts) are combinations of a compound of a IV-VIII group transition metal (catalyst) and an organometallic compound of a I-III group non-transition element (cocatalyst) An active center (AC) of polymerization in these systems is a compound (at the surface in the case of solid catalysts) which contains a transition metal-alkyl bond into which monomer insertion occurs during the propagation reaction. In the case of two-component catalysts an AC is formed by alkylation of a transition metal compound with the cocatalyst, for example ... 

Table 20. Polymerization of the Chromophore-Containing Monomers with Various Transition Metal Catalysts"...

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) ... 

A new class of substituted ionic polyacetylenes was synthesized by metathesis polymerization with transition metal-containing catalysts [77]. The monomers used were dihexyldipropargylammonium salts with bromide and tosylate as anions. It was found that MoClj-based catalytic systems were very effective for the cyclopolymerization of ionic monomers. The resulting dark red polymers exhibited good solubility in polar organic solvents such as methanol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), THE, and CHCI3, which indicates their ionic nature. The structure of the polymers was confirmed by IR, UV-visible, and H and NMR spectroscopy. Doping the polymers with I, resulted in a substantial increase of conductivity (10 S/cm) compared with the undoped state (10" S/cm). 

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