Surfactant-templated crystalline polygon nanoparticles of heterocyclic polypyrrole prepared with Fentonʹs reagent

Heterocyclic polymers such as polypyrrole (PPy) are normally amorphous and do not have morphological features when synthesized chemically. In this work, we report the crystalline polypyrrole nanoparticles showing hollow-centred polygon features synthesized through a chemical polymerization by using Fentonʹs reagent as oxidant and dodecylbenzenesulfonic acid sodium salt (DBS) as surfactant, dopant and template. SEM and TEM showed that the polygons are approximately 400–500 nm in size and about 50 nm in edge thickness. Dynamic study of the PPy formation process using TEM showed that the branched network featured crystal-like PPy units of about 20 nm in size. WAXD recorded a wide diffraction of the short-range order and a distinct diffraction of the long-range order. DSC revealed a strong, sharp endothermic peak of the PPy particles with the polygon morphology. Compared with the traditional oxidant ferric chloride, the PPy oxidized by Fentonʹs reagent also had slower polymerization rate, less DBS content, higher yield, and higher density and conductivity. A plausible mechanism was proposed to explain the formation of the observed particle morphology. This synthetic approach may be found useful to incorporate anionic biomolecules into other types of positively charged heterocyclic polymers.