Gloria Neculqueo

MONOESTERIFICATION OF STYRENE-MALEIC ANHYDRIDE COPOLYMERS WITH ALIPHATIC ALCOHOLS

Se han sintetizado copolimeros de anhidrido maleico-estireno en solucion acetona-tolueno a 60°C iniciado por azo-bisisobutironitrilo. Los copolimeros se han caracterizado por cromatografia de permeacion de geles y calorimetria diferencial de barrido. Se llevo a cabo la monoesterificacion de los copolimeros de anhidrido maleico-estireno con metano, etanol, n-propil, n-butil, n-hexil, n-octil alcohol y n-decil alcohol en tetrahidrofurano a 65°C, catalizada por 4-dimetilaminopiridina. El grado de esterificacion de los copolimeros se determino mediante FT-IR y fluctuo entre 68-85%. Un aumento de la velocidad de reaccion fue observada con el aumento de la cadena del alcohol. Las temperaturas de transicion vitrea de los copolimeros monoesterificados fueron tambien determinados y fluctuaron entre 242°C y 136°C para los copolimeros con metanol y n-decanol respectivamente

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.

MORPHOLOGICAL AND STRUCTURAL CHARACTERIZATION OF POLY(3-DECYLTHIOPHENE) PREPARED BY ELECTROPOLYMERIZATION USING 1-BUTYL-3-METHYL-IMIDAZOLIUMTETRAFLUORBORATE AS SOLVENT

In this paper, we report the electrochemical polymerization of 3-decylthiophene at room temperature using the 1-butyl-3-methylimidazoliumtetrafluorborate as solvent. The polymer film is electroactive and its morphology depends upon the anode used. The polymerized 3-decylthiophene was characterized by ft-infrared, uv-visible, thermal gravimetric analysis and conductivity measurement. 5, 7 and very stable polythiophene films can be deposited electrochemically on ITO glass or platinum electrode and can be switched very rapidly from highly doped to less doped states, with a strong change in absorbance and they have been investigated for use in various electro optical applications 8, 9 . Besides these properties, its environmental stability and good electrical and optical properties make the polyalkylthiophene very promising material. The use of a solvent of ionic type can be a great contribution in the obtaining of conducting polymers, since they have high ionic conductivities and are very stable. During the last 5 years a remarkable progress in the synthesis of ionic liquids has been achieved and now several companies offer these products on the market. In recent literature, electropolymerization of pyrrol 11 3,4-ethylened ioxythiophene 12 and benzene 13 have been reported. In this work, we present the polymerization of 3-decylthiophene by using 1-butyl-3-methyl-imidazoliumtetrafluorborate as solvent. In contrast with other electrochemical system used in this kind of monomers, no additional electrolyte is needed and the reaction can be carried out under mild conditions at room temperature. EXPERIMENTAL The 3-decylthiophene was prepared by the cross coupling reaction of the Grignard of 2-bromothiophene with 1-bromodecane, using the Ni(dppp) dichloride catalyst following the Kumada synthesis 14 . To an electrochemical cell of two compartments, separated by a fritted glass with a platinum anode 0.69 g. of 3-decylthiophene and 20 ml. of a mixture of the ionic liquid/dichloromethane, 50:50 were added under argon atmosphere. A constant current density of 2 mA/cm 2 was applied during 4 hrs. and a black-bluish film was deposited on the electrode. The film was removed from the electrode surface and washed thoroughly with acetonitrile, methanol and then dried under vacuum at 50oC during 6 hrs. 0.2 g (yield 28%) of the poly thiophene was obtained from the platinum electrode. The four point method for conductivity was performed on the film and was also characterized by FT-infrared, SEM microscopy, TGA and UV-visible.