In this research a comparative study of the starting unit chain length effect on the electropolymerization of thiophene or its oligomers was carried out considering mono (1Th), bi (2Th), ter (3Th), tetra (4Th) and sexi (6Th)-thiophene as starting units. The deconvolved transient allows stating that the growth of polythiophene (PTh) employing each of the starting units have the same predominant contribution to the nucleation and growth mechanism (NGM). The others contributions disappear as the length of the starting unit chain increase. The results were validated by scanning electron microscopy (SEM) of PTh deposits obtained onto SnO2 coated glass, following a potential pulse program. Besides of corroborating the electropolymerization model, this study suggested the possibility of designing and performing suitable experiments leading to the attainment of electro-deposited conductive polymers bearing a desired morphology, appropriated for prospective applications.

Neste trabalho foram estudados os mecanismos de nucleação e de crescimento (MNC) de camadas finas de policarbazol (PCz) depositadas por eletro-oxidação de carbazol em LiClO4 + acetonitrila anidra sobre um substrato de vidro coberto com SnO2, usando método potenciostático. Os transientes corrente-tempo (j-t) obtidos foram ajustados usando uma equação matemática que levou em conta três contribuições: a nucleação instantânea com crescimento bidimensional (IN2D) e tridimensional (IN3D) e, também, a nucleação progressiva com crescimento tridimensional (PN3D). No começo, a contribuição IN2D predomina mas, rapidamente, o processo IN3D passa a ser o mais importante. Para tempos de deposição t > 17 s, IN3D corresponde a 80% da corrente total. A visualização da morfologia da superfície das películas de PCz via microscopia eletrônica de varredura (SEM) concorda com o MNC proposto pelo método matemático. A película cobre muito rapidamente a camada de SnO2 que está relacionada ao processo bidimensional, 2D, mesmo que se observe alguma heterogeneidade distribuída aleatoriamente na película, proveniente do processo tridimensional, 3D. Após dois minutos de deposição, a rugosidade de toda a superfície dos depósitos corrobora a predominância dos processos 3D. Conseqüentemente, a informação obtida diretamente a partir dos transientes (j-t) é uma ferramenta muito conveniente e útil para predizer as condições de trabalho com o intuito de controlar o tipo de morfologia da película preparada por eletro-polimerização.

Polycarbazole (PCz) thin films have been deposited by electro-oxidation of carbazole in LiClO4 + anhydrous acetonitrile onto SnO2 coated glass substrates, by potentiostatic method and the nucleation and growth mechanism (NGM) were studied. The obtained current time transients (j-t) were fitted using a mathematical equation with three contributions: instantaneous nucleation with two-dimensional (IN2D) or three-dimensional (IN3D) growth, and also a progressive nucleation with three dimensional (PN3D) growth. At the beginning, the IN2D contribution is predominant but, quickly the IN3D processes become more important. At a deposition time t > 17 s the IN3D corresponds to 80 % of the total current. The visualization by scanning electron microscopy of the surface morphology of the PCz films is in agreement with the NGM proposed by the mathematical method. The film covers very rapidly the SnO2 under layer related to the 2D process, even if some heterogeneities randomly distributed in the films, issued from the 3D processes, are also visible. After two minutes of deposition, the roughness of the whole surface of the films corroborates the 3D processes domination. Therefore, the information directly obtained from the (j-t) transients is a suitable and very useful tool to predict the working conditions in order to control the type of morphology of the film prepared by electropolymerization.

Modified electrodes with o-phenylenediamine and p-benzoquinone copolymer were prepared optimizing the conditions to obtain a polymeric film with an adequate intake of copper. Various electrode materials were assayed, and the copolymer deposit was potentiodynamically prepared on a platinum electrode. The film thickness was varied with the number of potentiodynamic cycles. The wide potential window shown by this modified electrode allowed attempting the insertion of copper in the polymeric matrix using several strategies. The response of the electrode was checked in the presence of g-aminobutyric acid (GABA). This way it was possible to obtain an electrode with an adequate and reproducible response for the detection of GABA in the concentration range between 10-4-10-5 mole·L-1 being the reading stable after several measurements

Considering that electropolymerization process occurs via radical intermediates, it was used a stable nitroxide radical such as TEMPO, with the aim to stabilize the species generated in the electrode/solution interface. The obtained results show that TEMPO really acts as a "radical trapping". Therefore, applying an adequate electrochemical perturbation it should be possible the progressive elongation of polymeric chains, and with that, the control over the structure and polydispersity of the deposit

A serie of thiophene derivatives having functional groups of different nature between 2 and 2' ring positions has been synthesized. Through ab-initio calculations using HF 6-31G basis, the geommetry was optimized and the atomic distribution of the electronic densities of each neutral molecules were determined. It was found that the electronic density depends strongly on the nature of the atoms bonded to 2 and 2' ring positions. The electro-oxidation potential of the molecules was measured by cyclic voltammetry on platinum work electrodes. An inverse relation between the electronic density and the potential was found. The electrochemical oxidation of these compounds was irreversible and the voltammetric profiles showed assymetric peaks, which can be explain by the simoultaneous oxidation of the heterocyclic rings and the bridging functional groups

Se ha sintetizado una serie de derivados de tiofeno, que poseen grupos funcionales de diferente naturaleza puenteando las posiciones 2 y 2' de los anillos. Mediante cálculos ab-initio se han optimizado las geometrías y se ha determinado la distribución atómica de las densidades electrónicas que posee cada molécula neutra, empleando como base de cálculo HF 6-31G. Se ha encontrado que las densidades electrónicas dependen fuertemente de la naturaleza de los átomos unidos en las posiciones 2 y 2' de los anillos. Se determinó el potencial de electro-oxidación de las moléculas, por voltametría cíclica sobre electrodos de trabajo de platino, encontrándose una relación inversa entre la densidad electrónica y dicho potencial. La oxidación electroquímica de estos compuestos resultó irreversible y presentó picos voltamétricos asimétricos, los que son explicados por la oxidación simultánea del anillo heterocíclico y el grupo funcional que actúa como puente

Poly(p-phenylsulfonyl-aniline) have been synthesized by chemical polymerization from the respective monomer using copper perchlorate in CH3CN or potassium dichromate in HCl aqueous media as oxidizing agents. The products were characterized by elemental analysis, FT-IR, 1H-RMN, XPS, SEM and conductivity measurements. The FT-IR spectra of products synthesized in different media were similar. The XPS analysis shows that the polymer synthesized with potassium dichromate have groups sulfone, sulfoxy-hydroxyl and its equivalent radical. Moreover, it have 1% of covalent chlorine, which probably is incorporate by secondary adition reaction. The polymers shows electrical conductivity in the range of semiconduction.

Se sintetizó poli(p-fenilsulfonil-anilina) por polimerización química, a partir del monómero respectivo, usando como agentes oxidantes perclorato cúprico en CH3CN o dicromato de potasio en HCl acuoso. Los productos se caracterizaron por análisis elemental, espectroscopías FT-IR, RMN-1H y XPS, además de microscopía electrónica de barrido (SEM) y medición de conductividad. Los espectros FT-IR de los productos sintetizados en diferentes medios resultaron equivalentes. Sin embargo, el análisis por XPS mostró que el producto sintetizado usando dicromato de potasio en HCl acuoso posee grupos sulfona, sulfoxi-hidroxil y su radical equivalente. Además, presenta un 1% de cloro covalente, que se introduciría en la estructura por reacciones secundarias de adición a los anillos. Los polímeros tienen conductividad del orden de la semiconducción.