The lightly sulfonated poly(phenylene oxide) (SPPO) ionomers in different mixing solvents were emulsificated by water to form a series of waterborne microemulsions.The principle of emulsification was explained.The aggregated structure of SPPO chains in organic solvents was discussed.SPPO molecular chains can form a type of microionic lattice.The emulsification process included the dissociation of the microionic lattices and aggregation of the hydrophobic segments.The polarity of solvents was an important factor for the formation of stable microemulsion systems. The effects of properties of solvent systems

ionic contents and the type of counterions on phase inversion procedure weere discussed. The phase inversion processing during emulsification of SPPO ionomers was characterized by measuring the variatio of conductivity

viscosity and surface tension with addition of water. The mechanism of the phase inversion during emulsification of SPPO ionomers was also discussed.