High molecular weight polymers ferrocenes

The radical homo- and copolymerization of the ferrocene-containing monomer 154 allowed for the isolation of polymers containing pendent ferrocene moieties (Scheme 2.41).228 High molecular-weight polymers were obtained from AIBN-initiated reactions, whereas other cationic initiators gave only low molecular-weight materials. Electrochemical studies showed that homopolymer 155 underwent two oxidations at Ey2 = —0.13 V and Ey2 = +0.05V in... 

The development of processible high-molecular-weight polymers with skeletal transition metal atoms, as present in ferrocenes, represents a synthetic challenge, and a variety of materials with novel electrical, optical and magnetic properties can be expected . In this context, polymers containing repeating ferrocenyl units are of great interest. Some representative examples are listed in Scheme 18. 

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. 

Finally, the polymers produced from the ROP reactions, which are very rare examples of high molecular weight, well-defined polymers with skeletal transition metal atoms held in close proximity to one another, are of considerable interest with respect to their properties and possible applications (93). The most promising materials derived from [1]- or [2]metallo-cenophanes appear to be the poly(ferrocenylsilanes) which are easy to prepare from the readily available starting materials, ferrocene and di-chloroorganosilanes, of which many are provided by the silicone industry. Although the main features of these polymers appear to have been elucidated, much detailed work remains to be done to fully understand the characteristics of these unusual materials. It is expected that many interesting developments will result in the near future from studies of the... 

In the 1980s, the successful synthesis of elastomeric polyamides 120 of high molecular weight (d/n =10,000-18,000) was reported from the polycondensation of l,l -bis(/ -aminoethyl)ferrocene with diacid chlorides (Scheme 13). Also, polyureas 121 were prepared from the same ferrocene monomer and diisocyanates, and polyesters and polyurethanes were prepared from l,l -bis(/ -hydroxyethyl)ferrocene. However, the latter materials had much lower molecular weights and were characterized only by scanning electron microscopy. X-ray, and IR analyses. The introduction of ferrocenes in which the functional groups are separated from the cyclopentadienyl ring by at least two methylene units was crucial in order to reduce steric effects and to avoid the instability found previously in polymers of a-functionalized ferrocene due to the a-ferrocenyl carbonium ion stability. 

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