Browsing by Author "Diaz, FR"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
- ItemCarbazole-based electroluminescent devices obtained by vacuum evaporation(2001) D'Almeida, K; Bernède, JC; Ragot, F; Godoy, A; Diaz, FR; Lefrant, STransparent conductive oxide (SnO2)/organic layers/aluminum thin film sandwich structures were obtained by vacuum evaporation. The organic component was either a thin carbazole film or a bilayer. In that case, the carbazole film was deposited onto a thin insulating polymer film. The polymer used was the poly(tetrabromo-p-phenyleneselenide) (PBrPDSe). Photoluminescence measurements have shown that the carbazole thin films emit blue light. (I-V) measurements have shown that the structures exhibit diode characteristics. The forward direction is obtained when the transparent conductive oxide (TCO) is positively biased. However, the reproducibility of the results obtained with a single carbazole layer is poor. It appears that the stability of the sample is improved when a thin PBrPDSe film (40 nm) is introduced between the carbazole and the SnO2. The polymer film avoids the short circuit effect. In that case, the turn-on voltage of the diode is about 3 V, when the thickness of the carbazole film is around 250 nm and the electroluminescence appears at a voltage of about 5 V. It is shown that the thermionic effect cannot be used to explain the I-V characteristics, which are interpreted with the help of the Fowler-Nordheim tunnel effect. (C) 2001 John Wiley & Sons, Inc.
- ItemEvaporated thin films of insulating poly-(tetrabromo-p-phenylenediselenide)(PERGAMON-ELSEVIER SCIENCE LTD, 2002) D'Almeida, K; Bernede, JC; Godoy, A; Diaz, FR; Mevellec, JY; Molinie, PIt 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) (FBrPDSe) 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.
- ItemPoly(p-phenylene-diselenocarbonate) and poly(p-phenylene-diselenothiocarbonate): New semiconducting polymers(1996) Diaz, FR; Godoy, A; Tagle, LH; Valdebenito, N; Bernede, JCNew polymers which contain selenium in the main chain have been synthesized. Poly(p-phenylene-diselenocarbonate) and poly(p-phenylene-diselenothiocarbonate) have been studied by X-ray photoelectron spectroscopy (XPS). Electrical conductivity was measured on samples without dopant agent and on samples doped with AlCl3, FeCl3, SbF5 and I-2. The morphology of these compounds was studied using a scanning electron microscope (SEM). Copyright (C) 1996 Elsevier Science Ltd
- ItemSmectic Cu(II), Pd(II) and VO(IV) complexes: Synthesis, EPR and thermogravimetric studies(TAYLOR & FRANCIS LTD, 1998) Diaz, FR; Valdebenito, N; Serrano, JL; Marcos, M; Martinez, JI; Alonso, PJThe octadecanoate of N-(4-hexyloxyphenyl)salicylaldimine and the corresponding Cu(II), Pd(II) and VO(IV) complexes were synthesized and studied. The compounds were characterized by IR, H-1 NMR, elemental and thermal analysis and polarized light microscopy. Thermogravimetric analysis and electronic spectra of the complexes are reported. Electron paramagnetic resonance (EPR) measurements were performed.
- ItemSynthesis and characterization of polyarylureas. I. Potentially semiconducting polymers(WILEY-BLACKWELL, 2001) Diaz, FR; Godoy, A; Moreno, J; Bernede, JC; Sanchez, CO; Opazo, A; Gargallo, LPolyarylureas were synthesized from the reaction between phosgene with aromatic diamines. Depending on the pH, the polyarylureas presented different colors when the solvent used was pyridine. The polyarylureas were characterized by IR spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy (XPS). To study the thermal stability of the polymers, a thermal degradation was performed between 35 and 700 degreesC. The polyarylureas decomposed above 350 degreesC. Without doping, polyarylureas are considered as semiconductors [sigma = 10(-9) (Omega cm)(-) (1)]; after doping with I-2, their electrical conductivity increases by several orders of magnitude. (C) 2001 John Wiley & Sons, Inc.
- ItemThermal studies of poly(esters) containing silicon or germanium(SOCIEDAD CHILENA DE QUIMICA, 2001) Tagle, LH; Diaz, FR; Opazo, AThe thermal properties of poly(esters) containing silicon or germanium in the main chain and derived from the diphenols bis(4-hydroxyphenyl)-diphenylsilane and bis(4-hydroxyphenyl)-diphenylgermane and isophthaloyl or terephthaloyl acid dichlorides were studied by differential scanning calorimetry and dynamic thermogravimetry. Poly(esters) derived from terephthalic acid showed higher Tg and thermal stability values than those derived from isophthalic acid. Poly(esters) containing Ge showed higher Tg values but lower thermal decomposition temperatures when compared with the analogous with Si.
- ItemThermogravimetric analysis of poly(ester-carbonates) and poly(ester-thiocarbonates)(GORDON BREACH SCI PUBL LTD, 1995) Tagle, LH; Diaz, FRThe thermogravimetric behaviour of poly(ester-carbonates) and poly(ester-thiocarbonates) derived from the diphenol esters 4-hydroxy-phenyl-4-hydroxy-benzoate, 3-hydroxy-phenyl-4-hydroxy-benzoate, 4-hydroxy-phenyl-3-hydroxy-benzoate, and 3-hydroxy-phenyl-3-hydroxy-benzoate with phosgene and thiophosgene was studied by dynamic thermogravimetry. The thermal decomposition temperatures were determined, showing that poly(ester-carbonates) are more stable than poly(ester-thiocarbonates). The kinetics parameters, activation energy, reaction order and pre-exponential factor, were determined by using the Arrhenius relationship and a computer program.
- ItemThin amorphous platinum films photochemically obtained, and their potential use as modified electrodes(ELSEVIER SCIENCE SA, 2002) Tejos, M; Schrebler, R; Diaz, FR; del Valle, MAThin amorphous nanostructured Pt films have been photochemically obtained by means of direct UV radiation (254 nm) of an amorphous Pt[CH3(CH2)(8)COCHCOC4H9](3)K film deposited on Si(100) and on ITO glass through the spin-coating technique. The product of this photolysis was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and microanalysis. After that, the film was subject to cycles for 1 h, between -0.30 and 1.20 V, in a 0.50 M H2SO4 electrolytic solution. It may be observed that the peak potential shifts in approximately 0.04 V towards less positive values for the modified system, if compared with the platinum bulk. It only showed one peak in the hydrogen discharge if compared with the two peaks in the Pt bulk. Based on these data, the ITO/Pt modified system was tested as an electrodic substrate for aniline polymerization in 0.50 M H2SO4. The polymeric deposit was obtained at lower potentials than those required when the Pt bulk is used as an electrode. (C) 2002 Elsevier Science B,V, All rights reserved.
- ItemVinyltrimethylsilane-co-N-vinyl-2-pyrroline and vinyltrimethoxysilane-co-N-vinyl-2-pyrrolidone copolymers - Synthesis and reactivity ratios(1998) Gatica, N; Diaz, FR; Gargallo, L; Radic, DCopolymers containing vinyltrimethylsilane and vinyltrimethoxysilane with N-vinyl-2-pyrrolidone at different compositions were synthesized and characterized. The reactivity ratios was estimated by using the classical Fineman-Ross and Kelen Tudos linear fitting procedures. These parameters were also estimated through a computer program based on nonlinear minimization algorithm, starting from the r(1) and r(2) values obtained by the former procedures. The analysis of the results allow us to interpret the reactivity behaviour of these polymers in terms of the relative reactivity of the substiuents. The effect of the chemical structure of the polymer side group is discussed in terms of the different contributions to the stabilization of the radical intermediates.