Electroresponsive microgel able to form a monolayer on gold through self-assembly

Abstract

We present a novel microgel with the capacity for self-assembly, the volume of which can be altered by performing the appropriate redox reaction. The initial thermoresponsive microgel was synthesized from N-isopropylacrylamide and N-(3-aminopropyl)methacrylamide, with N,N′-bisacryloylcystine used as the crosslinker. The obtained microgel polymer network was modified with benzoquinone through the Aza-Michael addition reaction. The influence of the redox state of the benzoquinone groups in the microgel on volume phase transition temperature was examined. The disulfide bridges from the N,N′-bisacryloylcystine linker were used to attach microgel particles on an Au electrode surface, forming a monolayer. The monolayer formation and the volume phase transition within the microgel were monitored with the QCM technique. The redox state of the electroactive benzoquinone groups in the polymer network appeared to be the key factor determining whether the microgel layers exist in the shrunken or swollen state. The oxidation state can be changed electrochemically and the shrinking-swelling transformation was shown to be reversible. The obtained material was also studied with dynamic light scattering technique and electron microscopies.