Electron-induced growth mechanism of conducting polymers: a coupled experimental and computational investigation.

Pulse radiolysis was used to study the mechanism of HO(•)-induced polymerization of poly(3,4-ethylenedioxythiophene), PEDOT, in aqueous solution. A step-by-step mechanism has been found which involves a recurrent oxidation process by HO(•) hydroxyl radicals produced by water radiolysis. Furthermore, the cation radical, EDOT(•)(+), has been proposed as the promoter of the first step of polymerization. The determination of rate constants values and the attribution of transient and stable species were confirmed by molecular simulations and spectrokinetic analysis. Moreover, applying a series of electron pulses enabled in situ PEDOT polymerization. These polymers, which were characterized in solution or after deposition, form globular self-assembled structures with interesting conducting properties. Such a synthesis initiated for the first time by an electron accelerator gives us a glimpse of future promising industrial applications in the field of conducting polymers synthesis.

Radiolytic method as a novel approach for the synthesis of nanostructured conducting polypyrrole.

In this study, a novel and extremely facile method for the synthesis of conducting polypyrrole (PPy) was achieved in aqueous solution. This radiolytic method is totally free of template and environmentally friendly compared with traditional chemical methods. According to ultraviolet-visible (UV-vis) spectroscopy and Fourier transform infrared (FTIR) spectroscopy analysis, pyrrole (Py) monomers were polymerized into PPy thanks to their oxidation by HO(•) radicals produced by the radiolysis of water when exposed to γ irradiation. The morphology of PPy was characterized by cryo-transmission electron microscopy (cryo-TEM) in aqueous solution and by scanning electron microscopy (SEM) after deposition. In an original way, high-resolution atomic force microscopy, coupled with infrared nanospectroscopy, was used to probe the local chemical composition of PPy nanostructures. The results demonstrated that spherical and chaplet-like PPy nanostructures were formed by γ-radiolysis. Thermogravimetric analysis (TGA) and electronic conductivity measurements showed that radiosynthesized PPy had good thermal stability and an electrical conductivity higher than that of chemically synthesized PPy.

Radiation-induced synthesis of nanostructured conjugated polymers in aqueous solution: fundamental effect of oxidizing species.

Synthesis of conjugated poly(3,4-ethylenedioxythiophene) (PEDOT) polymers is achieved through the radiolysis of N2O-saturated aqueous solutions of 3,4-ethylenedioxythiophene by using two different oxidizing species: HO(·) (hydroxyl) and N3(·) (azide) radicals. Both oxidative species lead to self-assembled polymers that are evidenced in solution by cryotransmission electron microscopy and UV/Vis absorption spectroscopy and, after centrifugation and deposition, by scanning electron microscopy and attenuated total reflectance FTIR techniques. Whereas HO(·) radicals lead to PEDOT-OH globular nanostructures with hydrophilic properties, N3(·) radicals enable the formation of amphiphilic PEDOT-N3 fibrillar nanostructures. These results, which highlight the differences in the intermolecular interaction behaviors of the two kinds of PEDOT polymers, are discussed in terms of polymerization mechanisms.