One-step fabrication of hierarchical polypyrrole microspheres with nanofibers as building blocks

Hierarchical polypyrrole microspheres, which have nanofibers as building blocks, the size of several microns and a conductivity of 0.8 S cm−1, were prepared simply and directly via a one-step self-assembly approach in the presence of (NH4)2S2O8 (APS), cetyltrimethylammonium bromide (CTAB) and sulfonated polyaniline (SPANI). It was found that the formation probability of hierarchical polypyrrole microspheres depended on the (NH4)2S2O8/CTAB and SPANI/CTAB molar ratio. Bulk quantities of hierarchical polypyrrole microspheres can be obtained readily under the optimal conditions such as (NH4)2S2O8/CTAB molar ratio >2.8 and SPANI/CTAB molar ratio >4.7 × 10−3. The precipitate [(CTA)2S2O8] of CTAB and (NH4)2S2O8 was proposed to act as a “template” to promote the formation of PPY nanofibers, while the dopant SPANI was suggested to play a “rope-like” or “bridge-like” role in the subsequent self-assembly of nanofibers into PPY hierarchical microspheres. The experimental results and our investigation for the formation of PPY hierarchical microspheres may shed some light on preparing of other conductive hierarchically materials by proper molecular design and experimental condition optimization.