ResumenEn este trabajo se reproduce el fenómeno del espín semientero de la ejemplificación que hizo Paul A. M. Dirac con un par de tijeras, una cuerda elástica y una silla. Se describen tres ejemplos más en el que aparece el mismo fenómeno y se relaciona la estructura algebraica de los cuaternios con uno de los ejemplos. Se describen los resultados básicos de las estructuras algebraicas de los cuaternios H, y se establece una relación intrínseca con el fenómeno espín semientero y las matrices de Pauli.

AbstractIn this paper the phenomenon of half-integer spin exemplification Paul AM Dirac made with a pair of scissors, an elastic cord and chair play. Four examples in which the same phenomenon appears and the algebraic structure of quaternions is related to one of the examples are described. [20] Mathematical proof of the phenomenon using known topological and algebraic results are explained. The basic results of algebraic structures are described quaternions H, and an intrinsic relationship with the phenomenon half-integer spin and the Pauli matrices is established.

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.

Os efeitos da concentração do monômero e do hexafluorfosfato de tetra butil amônio nos processos de nucleação e crescimento do polifurano no eletrodo de disco de Pt na presença de CH3CN foram estudados pelo método de passos de potencial. Os valores transientes de j/t foram ajustados usando uma equação matemática que considera diferentes contribuições. No primeiro estágio de transição (0 < t < 20 s) não há contribuições correspondentes aos mecanismos IN2D e IN3D controlados por troca de carga, e do mecanismos PN3D sob controle de difusão. Os parâmetros analisados têm efeito distinto nas contribuições envolvendo os processos de nucleação e crescimento. No entanto, dependendo da concentração do monômero, a contribuição sob difusão controlada pode ser de maior ou menor importância, o que confirma a formação de uma "região oligomerica" na interface, durante o processo de polimerização.

The effects of monomer and tetrabuthylammonium hexafluorophosphate concentration on the nucleation and growth processes of polyfuran on Pt disc electrode in CH3CN have been studied through the step potential method. The j/t transients were fitted by means of a mathematical equation that considers different contributions. At the first stage of the transient (0 < t < 20 s), there are three contributions corresponding to IN2D and IN3D mechanisms controlled by charge transfer, and PN3D mechanism under diffusion control. The analyzed parameters have a distinct effect on the contributions involved in the nucleation and growth processes; however the IN3D mechanism was always the most important contribution. Nevertheless, depending on the monomer concentration, the contribution under diffusion control can be more or less important, which confirms the formation of an "oligomeric region" in the interface, during the polymerization process.

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.