Electroactuation of alkoxysilane-functionalized polyferrocenylsilane microfibers.

Cross-linked conductive polymer networks that mediate chemical, electronic, optical, and mechanical signals are enticing materials from which to construct actuators and sensors as well as more complex polymer-fiber-based structures capable of emulating natural cytoskeletal stress fibers such as actin. In this work we have synthesized and characterized a novel class of high molecular weight electroactive polyferrocenylsilane (PFS) that has been functionalized with pendant alkoxysilane groups and which can be conveniently gelled by sulfonic acid catalyzed condensation of the cross-linkable alkoxysilanes. These PFS electroactive gels are capable of converting an electrical signal to mechanical stress and strain as a result of a change in dimension in response to electrochemical oxidation or reduction coupled with transport of charge balancing ions and solvent molecules in PFS. Electrospinning of these polymer solutions is possible using a 5 kV voltage applied between a needle and indium tin oxide (ITO) substrate on to which fibers are collected. ITO substrates with collected fibers thereupon are incorporated into miniature electrochemical cells containing lithium triflate/gamma-butyrolactone electrolyte and examined using optical microscopy. Applying 1.5-2.0 V anodic potential to the ITO results in immediate oxidation of PFS fibers followed by strain induced buckling. This buckling occurs in many cases as regular sinusoid perturbations along the fiber. Application of cathodic 2.0 V potential causes most of the distorted fibers to return to their initial form. Such inherent shape memory is potentially useful in creating microswitches, microactuators, and micromanipulators.