Polyaniline/silica hybrid composite gels prepared by the sol-gel process

The preparation of polyaniline/silica hybrid gel was studied by chemical polymerization of aniline with sodium dodecyl sulfate (SDS) during the sol-gel processing. As a typical procedure, aqueous solutions of SDS, aniline, HCl, and tetramethoxysilane (TMOS) were mixed. Then ammonium peroxodisulfate (APS) in an acidic aqueous solution was added as initiator oxidant into the sol-gel systems at different sol-gel stages: (A) just after mixing (sol), (B) after gelation (wet gel), and (C) after 7 d (dried gel). As for the condition (A), several green areas and several tens of dark green spots with absorption peaks at 343, 422, and 802 nm were seen in the xerogel, indicating that emeraldine salt type polyaniline is aggregated in the silica xerogel. Polymerization of aniline little occurred in the dried gel (C), possibly because APS could not soak the silica pores and/or aniline could not polymerize in the gel. The xerogel from (B) showed a homogeneously green color with peaks at 339, 425, and 769 nm, showing that emeraldine salt type polyaniline can be uniformly dispersed in sol-gel silica.