Y. Tregouet

Electroluminescent polycarbazole thin films obtained by electrochemical polymerization

Abstract Polycarbazole (PCZ) thin films have been electrochemically synthesized on SnO 2 coated glass substrates. The electrolyte used was the anhydric LiClO 4 . It is shown that, after optimization of the potential scanning domain, PCZ films are systematically obtained. The physical and morphological properties of films are described. The films obtained with LiClO 4 as electrolyte are homogeneous and their coverage efficiency on the SnO 2 underlayer is very high. Films are exempt of pinholes, cracks and other morphological defaults as shown by scanning electron microscopy. Cyclic voltammograms are reversible, attesting the high quality of the structural properties of the films. Moreover these films are photoluminescent. After deposition of an aluminum upper layer, the structures SnO 2 /PCZ/Al behave like diodes with a forward polarization when the SnO 2 electrode is positively biased. Also these structures exhibit electroluminescent properties.

Synthesis, characterization and electrical properties of dihalogenated polyanilines

Abstract Poly(2.5-dichloroaniline), poly(2,3-dichloroaniline), poly(3,5-dichloroaniline), poly(2,5-dibromoaniline) and poly(2,6-dibromoaniline) have been synthesized from dihaloanilines in protic and aprotic media with different oxidizing agents, such as copper perchlorate, potassium dichromate and potassium permanganate. Each polymer is characterized by elemental analysis, IR and UV-Vis spectroscopy, scanning electron microscopy (SEM) and conductivity measurements. To obtain the doped polymers, they are treated with inorganic acids and then their electric properties determined. The use of different oxidants allows the obtention of polymers with different redox states which, in some cases, present semiconducting properties and are soluble in methanol and acetone. For the sake of comparison of the electrical and structural properties of the new polymers, polyaniline (PANI) has also been synthesized in a manner analogous to the poly(dihaloanilines).

Polycarbazole obtained by electrochemical polymerization of monomers either in solution or in thin film form

Polycarbazole has been synthesized by electrochemistry. The carbazole monomer source consists either in carbazole in solution in the electrolyte or in carbazole deposited in thin film form onto the working electrode. The two families of polymers have been studied by infrared absorption, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, electron spin resonance, and electrical conductivity measurements. It is shown that the polycarbazole films obtained with carbazole deposited in the thin film form exhibit a better polymerization efficiency and an electrical conductivity one order of magnitude higher. This result is in good accordance with a higher spin density and homogeneity. It is proposed that not only are some monomers activated during the evaporation but also that the physical contact between the working electrode and the continuous carbazole films induces the growth of homogenous highly polymerized polycarbazole films. In agreement with this suggestion, the SEM study shows that this type of polycarbazole thin films keep in memory the morphology of the SnO2 under layer.

Synthesis, characterization and electrical properties of poly[bis-(2-aminophenyl)disulfide] and poly[bis-(2-aminophenyl)diselenide]: Part II. XPS, ESR, SEM and conductivity study

Abstract Poly[bis(2-aminophenyl)disulfide] (DSDA) and poly[bis(2-aminophenyl)diselenide] (DSeDA) were synthesized by monomer oxidation with ammonium persulphate at different polymerization times, in 0.5 M H2SO4 and 1 M HCl media. X-ray photoelectron spectroscopy (XPS) analysis of DSDA shows similar percentage of imine and amine groups in the polymer, like emeraldine. DSeDA shows different percentages of imine and amine groups, which corresponds to a state different of emeraldine. When the time of polymerization of DSDA is increased, a small change in the oxidation state is detected, but in DSeDA the number of imine groups decreases. When polymerization is carried out in HCl media, both polymers present a minimum percentage of chlorine unit with covalent linkage to macromolecule. Moreover, electron spin resonance (ESR) study shows the presence of nitrogen and carbon radicals in the structure, and both radicals should be associated to chlorine or sulfate ions. The two polymers present low level of conductivity related to low level of doping. The macromolecules present a granular structure, but DSeDA is more pulverulent.

On the degradation of some thiophene oligomers after doping by ion chloride

FeCl3-doped thiophene oligomers (bi, ter, tetra, penta) in the powder form have been characterized by photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electron microprobe analysis, visible optical absorption, infrared absorption (FTIR) and electron spin resonance (ESR). The results show that even if the powders are only lightly doped, the chlorine dopant is only partly ionized (80 at.%). The positive charge induced by doping cannot be localized on sulphur, but probably can be localized on carbon. Since the doping is not large, the signal may be too small on sulphur to be detected by XPS, however, the ESR signal cannot be attributed to the S radical and we can imagine that the positive charge induced by doping is localized on carbon. The distribution of the dopant in the powder is not homogeneous. All the experimental results show that while the doping is not strong it has many consequences for the properties of the powder. The main one, corroborated by all the experiments, is that after doping there is a degradation of the bi- and terthiophene. We no longer have any bi- and terthiophene but x-thiophene with x ≥ 5; tetra- and pentathiophene are not modified.

Change with time of the properties of poly(seleno-p-naphthalene diamine) doped with chlorine

Abstract After synthesis, poly(seleno- p -arylene diamine) has been doped with chlorine. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) have been carried out on the doped powder. The changes in the experimental results with storage time have been systematically analyzed. It is observed that, relative to carbon, the atomic percentage of oxygen increases with time while the signals of N, Cl and Se decrease. The changes in the N1s and Se3d spectra show that the polymer is progressively decomposed by chlorine. This decomposition is in good agreement with the change in the ESR signal. These modifications can explain the decrease in conductivity with increasing storage time.

SINTESIS, CARACTERIZACION y PROPIEDADES ELECTRICAS DE POLI(p-FENILSULFONIL-ANILINA)

Se sintetizo poli(p-fenilsulfonil-anilina) por polimerizacion quimica, a partir del monomero respectivo, usando como agentes oxidantes perclorato cuprico en CH3CN o dicromato de potasio en HCl acuoso. Los productos se caracterizaron por analisis elemental, espectroscopias FT-IR, RMN-1H y XPS, ademas de microscopia electronica de barrido (SEM) y medicion de conductividad. Los espectros FT-IR de los productos sintetizados en diferentes medios resultaron equivalentes. Sin embargo, el analisis por XPS mostro que el producto sintetizado usando dicromato de potasio en HCl acuoso posee grupos sulfona, sulfoxi-hidroxil y su radical equivalente. Ademas, presenta un 1% de cloro covalente, que se introduciria en la estructura por reacciones secundarias de adicion a los anillos. Los polimeros tienen conductividad del orden de la semiconduccion.

Properties of poly(tetrabromo‐p‐phenylenediselenide) doped with IBr, H2SO3, and CH3COOH acids

Poly(tetrabromo-p-phenylenediselenide) (PBrPDSe) has been doped by IBr, H 2 SO 3 and CH 3 COOH acids. The samples have been studied by X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR). Conductivity measurements have also been performed on pressed pellet samples. It has been shown by XPS and ESR that, after doping, positive charges are localized on Se atoms. The conductivity of the acid-doped PBrPDSe exhibits an increase by about four orders of magnitude. However, the limit of 10 -7 Ω -1 cm -1 appears difficult to overcome. This saturation effect could be attributed not only to charge localization on Se atoms but also to steric hindrance related to the substituent introduced on the backbone of the polymer.

About some properties of terthiophene thin films otained in the presence of a red hot wolfram filament

Summary Terthiophene powder was synthesised following the cross-coupling Grignard reaction. A tungsten crucible with a multiholed cover was used to evaporate the powder under vacuum. A red-hot wol fram filament is placed between the evaporation source and the substrates. The variations of the properties of the deposited films were studied using the evaporation rate and the filament temperature as parameters. It is shown that there is some activation of the terthiophene by the hot wolfram filament.

Study of the effect of acid doping on the properties of poly(N-seleno-p-phenylene diamine)

Abstract Poly( N -seleno- p -phenylene diamine), before and after doping, has been studied by infrared absorption. X-ray electron spectroscopy (XPS), electron spin resonance (ESR) and room temperature conductivity measurements. The dopants used were inorganic (HCl, H 2 SO 4 ) and organic (CF 3 COOH, CH 3 SO 3 H, CH 3 OOH) acids. It is shown by IR absorption that only the CH 3 COOH doping does not systematically destroy the C-N and/or the N-Se-N bonds. The XPS analysis shows that some oxygen is present in the polymer even before doping. This oxidation and the dissymmetry of the monomer can justify the presence of an ESR signal before doping. After doping with CH 3 COOH the increase in the ESR signal and conductivity can be attributed to polymer protonation. This is in good agreement with the new component of the N1s signal obtained by XPS which can be attributed to N + radicals. However, it is shown by XPS that when the CH 3 COOH concentration increases, the N-Se-N bonds are partly destroyed which can explain the decrease in the ESR signal and the conductivity.