Formation of surface-attached responsive gel layers via electrochemically induced free-radical polymerization

We report on the formation of hydrogel layers on conducting substrates via a simple electrochemical route. Free-radical polymerization is initiated by an electron transfer from the substrate to a redox-active initiator. Gels of the thermally responsive material poly-N-isopropylacrylamide (p-NIPAM) with a thickness between 25 and 250 nm were produced and characterized. The gels adhere well to the substrate. They show the characteristic swelling transition at 32 degrees C. Although the films appear homogeneous in optical microscopy, AFM images reveal a slightly heterogeneous, globular structure. The gels are permeable to small ions as evidenced by electrochemical experiments with gel-covered electrodes.