Thermo-Switchable Charge Transport and Electrocatalysis Using Metal-Ion-Modified pNIPAM-Functionalized Electrodes

Metal ions (Ag+, Cu2+, Hg2+) are incorporated into an electrolpolymerized, poly(N-isopropyl acrylamide), pNIPAM, thermosensitive polymer associated with an electrode using the breathing-in method. The ion-functionalized pNIPAM matrices reveal ion-dependent gel-to-solid phase-transition temperatures (28 +/- 1 degrees C, 25 +/- 1 degrees C, 40 +/- 1 degrees C for the Ag+, Cu2+, and Hg2+- modified pNIPAM, respectively). Furthermore, the ion-functionalized polymers exhibit quasi-reversible redox properties, and the ions are reduced to the respective Ag-0, Cu-0, and Hg-0 nanocluster-modified polymers. The metal-nanocluster-functionalized pNIPAM matrices enhance the electron transfer (they exhibit lower electron-transfer resistances) in the compacted states. The electron-transfer resistances of the metal-nanocluster-modified pNIPAM can be cycled between low and high values by temperature-induced switching of the polymer between its contracted solid and expanded gel states, respectively. The enhanced electron-transfer properties of the metal nanocluster-functionalized polymer are attributed to the contacting of the metal nanoclusters; in the contracted state of the polymers. This temperature-switchable electron transfer across a Ago-modified pNIPAM was implemented to design a thermo-switchable electrocatalytic process (the temperature-switchable electrocatalyzed reduction of H2O2 by Ag-0-pNIPAM).