A microemulsion system composed of butyl acrylate (BA) and water with a mixture of sodium 12-acryloxy-9-octadecenate (SAO) and octylphenoxypoly(ethoxyethanol) as an emulsifier was initiated by gamma-ray radiation at room temperature to polymerize and produce microporous polymeric materials. The morphology and swelling characteristics of the resulting polymeric materials were studied. It was found that they strongly depended on the composition (water content, crosslinker content, emulsifier content) of the precursor microemulsions. In addition, the swelling properties of the polymer so prepared were found to be sensitive to the pH of the swelling medium. The change in swelling behaviors of the polymeric materials is discussed in terms of the polyelectrolyte effect exhibited by the polymerized anionic emulsifier SAG.