Pickering emulsions stabilized with PANI-NP: Study of the thermoresponsive behavior under heating and radiofrequency irradiation

Abstract

Micrometric Pickering emulsions in 1-octanol or cyclohexane were stabilized with water-dispersible electroactive polyaniline nanoparticles (PANI-NP). The emulsions were characterized by optical and electronic microscopy as well as spectroscopic techniques. It was demonstrated that nanoparticles maintain their functional properties (e.g., pH sensitivity and electromagnetic absorption) in the emulsion. Furthermore, as a proof of concept, smart Pickering emulsions employing PANI-NP stabilized with a thermosensitive polymer (PNIPAM) were obtained. The thermal behavior of the obtained structures was evaluated by turbidimetric techniques and an IR camera. The thermoresponsive emulsions have shown an important increment of the local temperature (>12°C) under radiofrequency (RF) irradiation. Phase transition of PNIPAM induced by heating or RF absorption provokes the breaking of the emulsions. In this context, the proposed systems herein could induce endothermal reactions carried out in organic solvents. Besides, Pickering emulsions formed by using electroactive PANI-NP could be applied in several medical or industrial applications.