Redox-mediated flux control in functional paper

It is still a challenge to control the structure and functionality of a porous material in a way that its properties can be changed by external triggers. To this end, the combination of porous paper substrates with redox-responsive ferrocene-containing polymer brushes is a promising approach. Here, surface-initiated Atom Transfer Radical Polymerization (SI-ATRP) protocols for a ferrocenyl methacrylate derivative, i.e. (2-(methacryloyloxy)ethyl ferrocenecarboxylate) (FcMA), were applied. The redox-responsiveness of the polymer-modified paper substrate was shown by chemical means and Kelvin probe force microscopy (KPFM), while X-ray photoelectron spectroscopy (XPS) revealed insights into the oxidation states of the ferrocene moieties. The control over the oxidation state enabled the precise control over the material's wettability as shown by contact angle (CA) measurements and capillary rise tests. Thus, these redox-mediated functional papers open a variety of applications for microfluidic devices.