Synthesis of hydrophobic polyanilines as a light-responsive liquid marble stabilizer

Abstract Hydrophobic and electrically conductive polyanilines were synthesized by single-step aqueous chemical oxidative polymerization in the presence of a perfluoroalkyl dopant, heptadecafluorooctane sulfonic acid. The resulting polyanilines were extensively characterized with respect to their morphology, surface/bulk chemical composition, wettability by water, (photo)thermal properties and conductivity. Scanning electron microscopy indicated that the polyanilines consisted of flocs of primary particles with sizes from submicrometer to a few hundreds of micrometers. Contact angle measurement and X-ray photoelectron spectroscopy confirmed the presence of perfluoroalkyl dopant on the surface of the dried polyanilines, which led to a water-repellent character. The conductivity of the pressed pellets increased from 3.2 × 10 −3  S cm −1 to 1.4 S cm −1 as the dopant concentration used in the polymerization was increased, and the conductivities were higher than that of polyaniline synthesized in the absence of perfluoroalkyl dopant. The resulting polyaniline powder was able to function as a liquid marble stabilizer with photothermal properties. The liquid marble exhibited locomotion due to Marangoni propulsion on a planar water surface under irradiation with a near-infrared laser, and its transfer from water to solid surfaces was also achieved. The liquid marbles could be disrupted via an external stimulus to release their internal contents.