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, is 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 polymerization of 3-hexylthiophene in oxygen-free and oxygen-saturated dichloromethane solvent

We thank Jean-Michel Guigner (IMPMC, Université Pierre et Marie Curie, France) for Cryo-TEM experiments.As alternative radiolytic approach, the synthesis of P3HT was made possible thanks to the oxidation of 3HT monomers by chloromethyl and dichloromethyl radicals or by their corresponding peroxyl radicals in situ produced by dichloromethane solvent radiolysis. Under two different experimental conditions, in oxygen-free solution and in oxygen-saturated solution, two different polymers, “P3HTN2” and “P3HTO2” respectively, were successfully synthesized. Both produced materials were discerned by several analytical and spectroscopic techniques. UV–Vis absorption spectroscopy results showed that the radiolytic yield of 3HT oxidation in dichloromethane solvent is higher under O2 atmosphere. Indeed, a dose of 75 kGy was needed to polymerize 10 mM in 3HT under N2 atmosphere, meanwhile a dose of 35 kGy was sufficient to polymerize the same amount of 3HT under O2. The average molecular weight of P3HTO2was found higher than that of P3HTN2 as revealed by SEC chromatography analysis. Also, P3HTO2exhibits better thermal stability than P3HTN2. ATR-FTIR spectroscopy revealed the specific presence into P3HTO2 polymers of some functional groups such as carbonyl, hydroxyl and carboxyl moieties, which clearly explains the difference between the morphological structures of P3HTN2 and P3HTO2 as highlighted by cryo-TEM, SEM and AFM microscopies. Finally, both radio-synthesized P3HTN2 and P3HTO2 polymers were found characterized by remarkably significant conductive, electronic and optical properties

Optimal strategy based on radiation chemistry for facile and direct synthesis of poly(3-thiophene acetic acid) polymers in water and dichloromethane

In this work, synthesis of nanostructured conducting poly(3-thiophene acetic acid) (PTAA) polymers was developed by means of γ-induced oxidative polymerization of TAA monomers dissolved either in water or in dichloromethane. This synthesis was shown to be facile and directly feasible without any prior esterification of TAA and in the absence of oxidizing agents. Radiolytic yields of TAA oxidation as well as irradiation doses required for quantitative PTAA preparation were determined for each solvent. UV-Vis and ATR-FTIR spectroscopies demonstrated the successful formation of two PTAA polymers, so-called "PTAAH2O"and "PTAACH2Cl2". Size exclusion chromatography (SEC) highlighted convergent molecular weight values corresponding to approximately 13 monomer units. A similar behavior for both radio-synthesized PTAAs was monitored by thermogravimetric analysis (TGA). The morphological structures of PTAAH2O and PTAACH2Cl2 were analyzed in solution by Cryo-TEM and after deposition by SEM and AFM. Microscopic observations revealed the presence of two distinguishable nanostructures: nano-spherules of several hundreds of nanometers made of PTAAH2O and nano-granules of several tens of nanometers made of PTAACH2Cl2. Cyclic voltammetry analysis and the Tauc plot method were employed to calculate the electrical and optical band gaps. Both polymers possess similar electrical band gaps. However, PTAACH2Cl2 affords a lower optical band gap than PTAAH2O. Four-point probe measurements showed that the radio-synthesized PTAA polymers are characterized by interesting electrical properties: a higher electrical conductivity was nevertheless recorded for PTAACH2Cl2. This study highlights the powerful ability of the radiation chemistry-based methodology to lead, as a simple, versatile and reliable method, to nanostructured PTAA conducting polymers either in aqueous or organic solutions

Superior photocatalytic activity of polypyrrole nanostructures prepared by radiolysis in water and dichloromethane

International audienceConjugated polymers have emerged as very active photocatalysts under visible light. Among these materials, nanostructured polypyrrole (PPy) has recently been used as photocatalyst for degradation of environmental pollutants under UV as well as visible light. In the present study, we specifically explored the photocatalytic activity of conducting PPy synthesized by radiolysis, either in water (PPyH2O) or in dichloromethane solvent (PPyDCM), in the absence of any external dopant or template. The successful preparation of both kinds of conducting polymers was confirmed by complementary spectroscopic techniques and morphological characterizations. Besides, the photocatalytic activity of both materials was evaluated in the degradation of phenol as model pollutant in aqueous solution. PPyH2O as well as PPyDCM were found to exhibit remarkably high photocatalytic activity under both UV and visible light. These organic photocatalysts remain very stable after several cycles and thus, easily reusable. Interestingly, PPyDCM clearly appears as the most efficient photocatalyst due to its longer chain length, highly doped nature, lower optical band gap and extended absorption band from the UV to the near infrared region. The present work definitely validates radiation chemistry as an 2 alternative approach to synthesize conducting polymer-based photocatalysts. The obtained results also highlight that the radiosynthesized PPy, especially those prepared in dichloromethane, constitute promising candidates for photocatalytic depollution of water

Photocatalytic degradation of organic pollutant with polypyrrole nanostructures under UV and visible light

International audienc

Conducting polymer nanofibers with controlleddiameters synthesized in hexagonal mesophases

International audienceOil-swollen hexagonal mesophases resulting from the surfactant mediated self-assembly of a quaternarymixture of water, surfactant, co-surfactant, and oil, are versatile templates to synthesize anisotropicnanomaterials. Poly(diphenylbutadyine) (PDPB) polymer nanofibrous network structures were producedin the oil tubes of the mesophases by photo-induced radical polymerization using a chemical initiator orby gamma irradiation. The diameter of the nanofibers can be varied from 5 to 25 nm in a controlledfashion, and is directly determined by the diameter of the oil tube of the doped mesophases, proving thusa direct templating effect of the mesophase. The nanoIR technique allows chemical characterization andidentification of the polymer nanostructures simultaneously with morphological characterization. Cyclicvoltammetry has been used as an effective approach to evaluate both the energy level of the highestoccupied molecular orbital (HOMO) as well as the energy of the lowest unoccupied molecular orbital(LUMO) and the band gap of the PDPB. The conductivity of the PDPB nanostructures obtained by gammairradiation was estimated to be 0.1 S/cm, which is higher than the conductivity of PDPB nanostructurespreviously reported in the literature. The soft template approach allows size tunable synthesis of anisotropicpolymer structures with morphological homogeneity at the nanoscale with high conductivity, thus it appearsto be an attractive opportunity for electronic device applications

Atomistic simulations of spontaneous formation and structural properties of linoleic acid micelles in water

International audienceMolecular dynamics simulations were used to explore the structure of linoleic acid (LIN) micelles with 60 monomers in explicit water. To examine micellar properties, two approaches were considered using ‘preformed' and ‘self-aggregated' micelles. Our results demonstrate the quickness of the process of monomers aggregation. After 10 ns, both ‘preformed' and ‘self-aggregated' micelles are characterized by very similar structural properties: a slightly ellipsoidal shape and dimensions close to 20 Å. In addition, ‘preformed' and ‘self-aggregated' micelles display mainly hydrophobic surfaces, since these latter are made up of 73% of LIN tails. Finally, within the two kinds of micelles, LIN molecules are bent due to their cis double bond conformations

Photocatalytic degradation of organic pollutant with polypyrrole nanostructures under UV and visible light

Conjugated polymer nanostructures (CPNs) emerge as a new class of photocatalysts for organic pollutant degradation under UV and visible light. Polyprrole (PPy), as a conjugated polymer, exhibits a wide range of applications. We present here the first demonstration of employing pure PPy nanostructures as a very efficient photocatalyst for water depollution. PPy nanostructures were synthesized in hexagonal mesophases (used as soft templates) by chemical polymerization (PPy-NS-c), obtained by radiolysis (PPy-NS-gamma), and synthesized without any template via chemical method (PPy-bulk) as bulk. The different PPy samples were characterized by SEM, TEM, FTIR and UV vis absorption spectroscopy. The photocatalytic activity of both PPy nanostructures (PPy-NSc and PPy-NS-gamma), which remain very stable after several cycles, was evaluated for the degradation of organic pollutant in aqueous solution (phenol and methyl orange were taken as a model pollutant). PPy nanostructures show high photocatalytic activity under both UV and visible light while bulk PPy (PPy-bulk) has no appreciable activity. PPy-NS-c present the highest activity for photodegradation of phenol under UV light, while PPy-NS-gamma exhibit the best photocatalytic activity under visible light. We demonstrate here that the nanostructuration of these polymers is an important factor for their application in photocatalysis

Synthesis of Nanostructured Metal-Organic Films: Surface X-ray Radiolysis of Silver Ions Using a Langmuir Monolayer as a Template

An application of the radiolysis method using an X-ray synchrotron beam is developed as a novel approach to the synthesis of metal-organic films with controlled shapes and thickness. We demonstrate that a Langmuir monolayer deposited onto a silver ion containing subphase, irradiated by an incident beam impinging below the critical angle for total reflection, induces the synthesis of a stable nanostructured silver-organic ultrathin film at the air-water interface. The X-ray scattering is also used to monitor in situ the structure of the silver layer during the synthesis process. The layer is observed by atomic force microscopy after its transfer onto a silicon substrate. One observes a film thickness of 4.6 nm, in good agreement with the X-ray penetration depth, about 4.5 nm. The silver structure is oriented by the initial organic film phase. This experiment demonstrates the considerable potential of this approach to produce various controlled metal-organic films with a surfactant self-assembly as a template