Electrochemical Switching of Metallopolymer-Functionalized Indium Tin Oxide Derived by Cu^<b>0</b>-Mediated Atom Transfer Radical Polymerization

A redox-responsive polymer-modified indium tin oxide (ITO) was fabricated via a convenient filter paper-assisted Cu⁰-mediated surface-initiated atom transfer radical polymerization (FP-Cu⁰-SI-ATRP), enabling the formation of ferrocene-containing polymer brushes, poly-(2-(methacryloyloxy)-ethyl ferrocenecarboxylate) (PFcMA), with tunable thickness on ITO. By varying the monomer concentration, uniform polymer brushes with controllable thicknesses ranging from 10 to 122 nm were obtained. Compared to surface-initiated atom transfer radical polymerization (SI-ATRP), FP-Cu⁰-SI-ATRP achieved significantly higher polymerization rates, thicker films, and a shorter reaction time (5 h vs 20 h), while eliminating the need for subsequent metal catalyst removal. Characterization by Fourier Transform Infrared spectroscopy (FTIR), Ultraviolet-visible spectroscopy (UV-vis), atomic force microscopy (AFM), an ellipsometer, and water contact angle (WCA) measurements confirmed the successful grafting and systematic changes in PFcMA brush thickness and surface properties. Electrochemical performance, assessed by cyclic voltammetry (CV), revealed that thinner films exhibited efficient, diffusion-controlled redox behavior, whereas thicker films showed increased resistive effects. While the modified ITO prepared via SI-ATRP displayed lower redox activity despite having a similar thickness, this suggests a less favorable polymer brush morphology for charge transport. These findings establish FP-Cu⁰-SI-ATRP as a promising approach for constructing redox-active interfaces with tunable electrochemical properties for smart material applications.