Temperature and ionic strength modulated responses of modified with viologen derivative electrosensitive microgel

A new electroactive microgel was successfully synthesized. The starting material was a polymer based on N-isopropylacrylamide, sodium acrylate and the N,N'–methylenebisacrylamide crosslinker, which was functionalized with amine derivative of viologen. This two-redox-systems molecule was bound through the amide bond between the viologen amine group and the acrylate carboxylic group. A layer of the electroactive viologen-modified microgel was successfully attached to the Au Quartz-Crystal Microbalance with Dissipation (QCM-D) electrode surface using the "drop on" method. Electrochemical and gravimetric measurements indicated that the thickness of the p(NIPA-SA-V) microgel layer could be altered by three factors: temperature, ionic strength, and potential. Under optimal environmental conditions of 37 °C and low ionic strength, a fast and reversible thickness change from 400 to 250 nm was possible upon application of appropriate potential.