Enhanced electrochemical stimuli multilayers based on a ferrocene-containing polymer

Based on the noncovalent functionalization of ferrocene-grafted polyethylenimine (PEI-Fc) and carbon nanotubes (CNTs), CNT bundles are exfoliated by PEI-Fc solution and thus form stable compounds PEI-Fc@CNTs, which is used to construct the PEI-Fc@CNTs/DNA multilayers through layer-by-layer assembly. The multilayers show a highly uniform and homogeneous characteristic, which significantly improve the electrical property of the multilayers. Upon the oxidation electrical potential, the ferrocene groups are switched from reduction state ([Fe(C5H5)2]) to oxidation state ([Fe(C5H5)2]+), leading to change of microenvironments' charge density, resulting in swelling of the multilayers and a final degree of swelling of 37% and the decrease of multilayer stiffness. We maintain that electrochemical control over the swelling behavior of multilayers could have important implications for responsive coatings of nanoscale devices, including mechanically tunable surfaces which are used to modulate cellular activities and control drug delivery.