Ferrocene is a redox-active organometallic compound which can be incorporated into various monomers and used to make polymers which can be tethered onto a surface.  Vinylferrocene (ferroceneylethene) can be prepared by a Wittig reaction and then polymerized to form polyvinylferrocene (PVFc), an analog of polystyrene.  Another polymer which can be formed is poly( ferrocenecarboxylate), PFcMA.  Both PVFc and PFcMA have been tethered onto silica wafers and the wettability measured when the polymer chains are uncharged and when the ferrocene moieties are oxidised to produce positively charged groups, as illustrated at right.  The contact angle with water on the PFcMA-coated wafers was 70° smaller following oxidation, while in the case of PVFc the decrease was 30°, and the switching of wettability has been shown to be reversible.  In the PFcMA case, the effect of longer chains with more ferrocene groups (and also greater molar mass) has been investigated, and it was found that longer chains produce significantly larger contact angle reductions.