We have prepared porous microspheres of polyaniline and several of its mono- and di-substituted derivatives through a water-in-oil-in-water (W/O/W) double emulsion method. The double emulsion is generated by the rapid addition of excess 4M ammonium hydroxide to an acidic dispersion containing the preformed polymer and an amphiphilic monomer such as o-toluidine. The monomer is soluble in acidic solutions but spontaneously forms immiscible droplets in sufficiently alkaline solution. The polymer dissolves in the monomer droplets to form the spheres and pores are formed by water droplets trapped in the polymer matrix. The monomer serves as a single small molecular surfactant that stabilizes both the oil-water and water-oil interfaces of the double emulsion. This is rare among W/O/W systems, which typically require multiple surfactants and stabilizers. FTIR and NMR spectroscopy confirm the presence of the monomer in the polymer spheres and its absence in non-spherical particles. SEM images reveal that the initially granular polymers can be nearly fully converted into discrete porous spheres. We have applied this method to polyaniline, poly(o-toluidine), poly(m-toluidine), poly(2,5-dimethylaniline) and poly(3,5-dimethylaniline). Each material has been optimized by varying the amount of dispersed polymer and dissolved monomer. This has resulted in a catalog of porous conducting polymer microspheres with potential applications including pH and redox-active microreactors, scaffolds for catalysis, and encapsulants for cargo loading and delivery.

Porous microspheres of polyaniline and its derivatives prepared from single surfactant W/O/W double emulsions

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.