Polypyrrole Whelk-Like Arrays toward Robust Controlling Manipulation of Organic Droplets Underwater.

Whelk-like polypyrrole (PPy) arrays film is successfully prepared by electropolymerization of pyrrole in the presence of low-surface-energy tetraethylammonium perfluorooctanesulfonate (TEAPFOS) as dopant. The underwater wettability of PPy whelk-like arrays can be successfully tuned by electrical doping/dedoping of PFOS ions. Interestingly, CCl4 droplets with microliter-size as a representative sample are gathered together to form a larger droplet underwater at the potential of +0.8 V (vs Ag/AgCl), because PPy is in its PFOS-doped states. Note that CCl4 droplet can climb uphill successfully on the inclined whelk-like arrays PPy film under the applied potential of -1.0 V (vs Ag/AgCl), which may be attributed to wettability gradient derived from different oxidation states of PPy induced by electrochemical potential. These results may provide a simple strategy for on-demand manipulation of organic droplets underwater at low voltage.