DEVELOPMENT AND CHARACTERIZATION OF CATALYTIC ELECTRODES BASED ON CONDUCTING POLYMERS OF POLYPYRROLE AND POLYANILINE ON DIFFERENTS SUBSTRATES

	During the last years the development of textiles with new properties has been a very active field. For example textiles with thermoregulative properties have been created with microcapsules containing phase change materials, autocleaning textiles, textiles with hydrophobic coatings, etc. Another field that is being explored is the field of conducting textiles, which the present thesis treats about. Products based on conducting textiles have been created, for instance: a MP3 integrated in a jacket, dresses with LEDS, shirts to monitoring the conditions of the patients in the hospitals, etc. This sort of modifications in the textiles creates an extra value in the final product in addition to an increasing market that makes them very interesting in the present situation of the textile sector. It was estimated that for the year 2008, the field of the textiles to monitoring the conditions of the patients could represent a market between 100 and 1000 million dollars.

	To obtain conducting textiles, metallic fibers integrated in the textiles have been traditionally employed. The problem with the metallic fibers is that the movements of bending, twisting and stretching that take place in a textile break the fibers. The conducting polymers are employed as an alternative due to its flexibility and ease of synthesis above the fabrics. The chemical polymerization of pyrrole in the presence of textile substrates produce a uniform coating on the textile with a thickness of less than 1 µm.

	In the present work textiles of polyester covered with polypyrrole/ anthraquinone sulfonate (AQSA) and polypyrrole/ phosphotungstate (PW12O403-) have been obtained. The employment of counter ions with high size like the AQSA (organic) or the PW12O403- (inorganic) would prevent the expulsion of the counter ions (dedoping) from the polypyrrole structure, avoiding the loss of electrical and electrochemical properties. Once a conducting substrate was obtained (conducting textile), an electrochemical synthesis of conducting polymers (polypyrrole and polyaniline) could be performed. The electrochemical coating improves the electrical and electrochemical properties of the material. Conducting polymers have been employed in electrocatalysis for the removal of certain pollutants; this is why these materials could be employed in the electrochemical treatment of pollutants like organic dyes.

The conducting textiles obtained either chemically or electrochemically were characterized chemically, morphologically, electrically and electrochemically with the following techniques: Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), Energy Dispersive X-Ray (EDX), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), measurements of surface resistivity, Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Scanning Electrochemical Microscopy (SECM). The stability of the coatings was tested with washing and friction tests. Tests of the stability in different pH solutions were also performed to study the changes of the properties and to see the operational range where the conducting textiles maintain an acceptable electrical and electrochemical properties.

Moreover, polypyrrole powders not deposited on the textiles were characterized additionally with the following techniques to study its stability with the temperature: Electrochemical Impedance Spectroscopy with the temperature, Termogravimetry (TG), Differential Scanning Calorimetry (DSC), Pyrolisis/ Gas Chromatography/ Mass Spectrometry (Py-GC-MS). 

The conducting textiles showed values of surface resistivity in the range of 10^2 ohms/square, polyester presents values higher than 10^10 ohms/square; what represents a decrease of eight orders of magnitude in the surface resistivity. The chemical and morphological characterization demonstrated the presence of a uniform layer with good properties. In general the conducting textiles presented a good stability with washing tests and with the pH. The friction assay produced a loss of part of the coating, however only an increase of the surface resistivity lower than the expected was obtained. The electrochemical characterization demonstrated that the electrochemical synthesis produces more electroactive coatings. Moreover in the electrochemical synthesis of polyaniline it was observed that the method of synthesis (potentiodynamic or potentiostatic) influences the microstructure of the coating obtained. It was demonstrated that in the potentiodynamic synthesis the scan rate was an important parameter. With high scan rates (50 mV•s-1 y 5 mV•s-1) the polymer growth has been monitored with detail. In the first steps a coating with centipede-like morphology has been detected for polyaniline, this sort of morphology has not been obtained in bibliography for conducting polymers.