Electrochemical AFM on surface grafted poly(ferrocenylsilanes)

Ethylenesulfide and trimethylenesulfide end-functionalized poly(ferrocenyldimethylsilanes) (ES-PFS and TMS-PFS) with different degrees of polymerization were prepared via anionic ring-opening polymerization. Molecular characterization of ES-PFS was carried out by using 1H-NMR, GPC, FTIR, and elemental analysis. Thin films of ES-PFS were prepared by immersing gold(111) substrates into 1.0 mg/ml solutions of the polymers in toluene. The polymeric films were characterized by FTIR, XPS, and contact angle measurements. Thicknesses of the grafted films were measured by SPR. Thicknesses determined by SPR and the theoretically calculated values are in a reasonable agreement. The morphology of the films was studied by tapping mode AFM. The electrochemical behavior of the films was monitored by cyclic voltammetry (CV). CVs show two reversible redox peaks, indicating a stepwise oxidation of the iron atoms in the polymer chains. Scanning Electrochemical Force Microscopy (SEFM) allowed us to study in situ the morphological changes occurring in the film upon electrochemical oxidation or reduction. AFM images indicated that in the oxidized form the chains were stretched due to electrostatic repulsion