Polyferrocenylsilanes ferrocene polymers

Much of the interest in poly(vinylferrocene) arises from the presence of redox-active iron sites attached to the polymer chain. Cyclic voltammetry experiments [17,18] have revealed that the iron sites are non-interacting, as a single reversible oxidation wave is observed as the iron centers interconvert between Fe" and Fe states (Fig. 2.1). The intensity of the current per molecule is directly proportional to the molecular weight of the polymer sample [18]. The observation of a single cycUc vol-tammetric wave in solvents of low dielectric constant is in contrast to the situation for polymers in which the ferrocene units are in dose proximity in the polymer backbone, such as polyferrocenylsilanes (see Chapter 3, Section 3.3.6.3). For the latter materials, evidence for communication between iron centers is provided by the presence of two reversible oxidation waves. This has been explained in terms of oxidation of one Fe center making the neighboring Fe centers more difficult to oxidize. 

The Tg values of polyferrocenylsilanes, which can be as low as ca. -50 °C, are remarkable for a polymer structure with a bulky unit such as ferrocene in the main chain. Even when the influence of the side groups is small, the Tg values are still close to ambient temperature (e.g., for 3.22 (R=R = H), Tg=16°C). By contrast, the Tg of poly(vinylferrocene) is reported to be high (185 or 233 °C Chapter 2, Section 2.2.1.1). The ability of the iron atom in each ferrocene unit to act as a freely rotating molecular ball-bearing [106] probably plays a key role in generating the observed conformational flexibility in polyferrocenylsilanes. This aspect has been explored by means of variable-temperature solid-state NMR studies on PFSs 3.22, which were specifically deuterated either on the Cp rings or in the side groups [107]. 

PolyferrocenylsUanes are an interesting class of metal-containing polymers wiffi a mainchain consisting of alternating ferrocene and organosilane units. " Well-defined diblock copolymers containing polyferrocenylsilane segments are readily... 

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