P. Molinie

Synthesis and characterization of copolymer derived from poly-phenylene-vinylene potentially luminescent copolymers

Abstract The objective of the present work, described in this paper, is to synthesize and characterize new conjugated materials with tunable properties, as well as to contribute to a better understanding of their structure and physical properties. This copolymer, derived from poly-phenylene-vinylene (PPV), denoted PPV–ether is amorphous and insoluble in common solvents. It was characterized by infrared absorption (IR), Raman scattering, optical density (OD), gravimetric thermal analysis (GTA), differential thermal analysis (DTA), X-ray photoelectron spectroscopy (XPS) and photoluminescence. After synthesis and purification the copolymer PPV–ether is obtained with oligomer (F3), a fraction of copolymer, which is soluble. The results of GTA and DTA show that this copolymer is very stable. The IR, Raman scattering, and XPS studies show the good purity of the materials and confirm the proposed structure. The OD and photoluminescence (PL) measurements show that this copolymer can be exploited in optoelectronic applications.

Study of the evolution of the conductivity of iodine-doped poly(N-vinylcarbazole) as a function of annealing treatment

Electron spin resonance (ESR) and d.c. conductivity measurements on iodine-doped poly(N-vinylcarbazole) (PVK) as a function of annealing treatment was performed. When doped at room temperature as at 370 K, the appearance of an ESR signal and the increase of the conductivity can be explained by CT complex formation between iodine and PVK. The correlation between conductivity σ and spin density Ns was observed as a function of the annealing temperature. At higher annealing temperature, the decrease of the conductivity and of the ESR signal is attributed to the PVK degradation and to the formation of a new conjugated polymer. All these results and their discussion are in good agreement with X-ray diffraction, Raman diffusion, and earlier studies.

Mechanistic studies of reversible layer-type electrodes

Abstract In layered type intercalation electrodes ions are stored reversibly during the functioning of secondary batteries. The behaviour of the system depends on geometrical and electronic factors. The geometrical factors are concerned with the localization of the ions in the host structure; they deal with average structure determinations and local ordering problems. The diffusion properties of the intercalated ions depend on the site geometry, the population of the van der Waals gap, the ionicity of the bonds in the host, the stoichiometry of the host, and the mechanical properties of its slabs. Electrons have to be accommodated by the host. The band structure of the host plays an important role in respect of the ability to intercalate, the phase limit, and the stability of the products. Metal-insulator transition may be induced. Other possible factors such as Jahn-Teller effects have also to be considered.

Changes of the properties of poly-phenylene-vinylene-ether and C1-4 poly-phenylene-vinylene-ether with iodine pressure and annealing

Abstract It is shown by X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), infrared absorption (IR) and optical density (OD), that a charge transfer (CT) complex is formed between poly-phenylene-vinylene ether (PPV-ether) or C 1–4 PPV-ether and iodine. New more stable CT complexes are obtained with annealing at 463 K for PPV-ether and 353 K for C 1–4 PPV-ether. From IR, XPS and ESR analysis, we deduced that the doping mechanism of both co-polymers is a grafting of the iodine to the ether links. ESR analysis reveals that at this annealing temperature, 433 K for iodine doped PPV-ether and 463 K for iodine doped C 1–4 PPV-ether, a new radical center appears, added to the first radical centre.

Two new organic–inorganic complexes associating the radical anion ABTS·– and the inorganic cation Ca2+: Ca0.55(ABTS)(H2O)x and Ca5(ABTS)6(H2O)29

Abstract The synthesis, crystal structure determination and physical properties of two new charge transfer salts containing the azinobisethylbenzothiazoline (ABTS) anion are described. Electrochemical oxidation in water of the diammonium salt of ABTS in presence of calcium chloride yields black single crystals of two new compounds with different morphologies. The needle-like crystals with Ca0.55(ABTS)(H2O)x formula (x depending on the temperature) belong to the monoclinic symmetry, space group C2/c and cell parameters a=21.568(5), b=14.535(5), c=8.0278(17)xa0A, β=108.32(3)° at room temperature and a=22.180(4), b=14.288(3), c=8.0823(16)xa0A, β=108.13(3)°, with a lowering of the symmetry, space group Cc, at 200xa0K. The plate-shaped crystals formulated as Ca5(ABTS)6(H2O)29 belong also to the monoclinic symmetry with P21 space group and cell parameters a=11.222(2), b=37.991(8), c=19.327(4)xa0A, β=106.37(3)° at 200xa0K. The structure analysis of the first phase shows a one-dimensional character based on the stacking of organic molecules creating channels in which Ca2+ cations and water molecules are located. The second phase can be described as an alternation of organic and inorganic layers corresponding to a bidimensional hybrid network. The magnetic and electrical properties will be discussed.

About some properties of new poly(phenylene vinylene) derivatives: PPV-ether and C1-4PPV-ether

Abstract Although, the presence of the substituted groups induce a difference in physical and chemical properties of the co-polymer, it does not affect its symmetry group. We deduce from IR and RRS analyses of C1–4PPV-ether, compared to those of PPV-ether, that the geometrical structural modifications with a decrease in the planarity of the chain and the vibrational features are possibly ascribed to conformational effects. The molecular packing effect is also outlined. Moreover, the decrease of the optical gap and the higher energy shifted transition could be assigned to the different lattice relaxations and vibrational behaviors shown by this co-polymer. Added to IR, RRS and optical density results, the PL measurements prove a great delocalization of π-electron system with a red shifted emission.

Synthesis and characterization of C1–4poly-phenylene-vinylene–ether photoluminescent copolymers

Abstract In this paper, we describe a red-colored copolymer (C 1–4 poly-phenylene-vinylene–ether (C 1–4 PPV–ether)), which is insoluble in common solvents. It is characterized by infrared absorption (IR), Raman scattering, optical density (OD), gravimetric thermal analysis (GTA), differential thermal analysis (DTA), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). GTA and DTA results have shown that this copolymer is highly stable and decomposes above 570xa0K. Photoluminescence analysis has shown C 1–4 PPV–ether has some very interesting optical properties that might be very useful in optoelectronics.

Physico-chemical characterization of poly(seleno-p-arylene diamine)s doped with chlorine

Abstract After synthesis, poly(seleno- p -arylene diamine)s were doped with chlorine. The polymers were studied before and after doping by X-ray photoelectron spectroscopy (X.p.s), electron spin resonance (e.s.r.) and conductivity measurements. It is suggested that chain ends may be partly terminated by groups containing oxygen. After doping, there is charge transfer complex formation as shown by X.p.s. analysis. In some polymers, the e.s.r. study provided evidence that doping induces carbon radical formation. However, the conductivity remains quite low, whatever the material. This can be explained by small chain lengths and chlorine attack of the chains.

Evaporated thin films of insulating poly-(tetrabromo-p-phenylenediselenide)

Abstract It has been shown that thin insulating film at the interface transparent conductive oxide/organic electroluminescent film could improve the performance of organic electroluminescent diodes (OLED). Such insulating film can be inorganic or organic. Poly-(tetrabromo- p -phenylenediselenide) (PBrPDSe) has been proved to be an efficient insulating film in OLED. The properties of these evaporated PBrPDSe thin films have been systematically studied by IR absorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electron spin resonance and optical transmission measurements. It is shown that, when the deposition temperature is kept below the decomposition temperature of the polymer, tetrabromo- p -phenylenediselenide molecule is preserved during the deposition process. However the polymer, which is insoluble in powder form, becomes soluble after deposition. It can be concluded that films are mainly composed of oligomers of tetrabromo- p -phenylenediselenide. The electrical properties of SnO 2 /PBrPDSe/Al thin films structures have been studied. The current–voltage characteristics exhibit a rectifying behaviour with a forward direction corresponding to a positive bias of the transparent conductive oxide film, the SnO 2 .

Degradation of the electrical properties of chlorine-doped poly(seleno-p-arylen diamine)s

Abstract The changes in the conductivity of chlorine-doped poly(seleno- p -arylen diamine)s have been studied with temperature, storage time and ambient atmosphere. The samples have also been studied using X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR). The conductivity of the polymers with carbonyl in their backbone decreases with storage time but is insensitive to oxygen. The decrease in conductivity with time is attributed to the breaking of the Seue5f8N bonds by chlorine attack, which induces polymer degradation as shown by XPS. The conductivity of the polymers without carbonyl in their backbone was increased by oxygen. This increase can be attributed to oxidation of these polymers and to bipolaron formation as shown by ESR measurements.