METHODS: Granular poly(o-toluidine) (POT) was transformed into porous microspheres when ammonium hydroxide was added to an aqueous acidic dispersion containing the preformed polymer and amphiphilic o-toluidine (OT). The OT, POT, and ammonium hydroxide concentrations were varied to understand the formation mechanism. Conditions were optimized to obtain a narrowed size distribution.
RESULTS: The rapid change from acidic to alkaline surroundings produces a W/O/W double emulsion from POT and OT over a relatively narrow concentration range. Spheres form when POT dissolves in immiscible OT droplets, and entrapped water droplets form the pores. OT serves as the single amphiphilic surfactant and dissolved POT serves as a hydrophobic co-stabilizer. o-Toluidine, m-toluidine, or p-toluidine could be used as the single surfactant to obtain porous spheres from preformed POT, PANI and poly(m-toluidine).