Propriedades eletroquimicas e eletrocromicas de poli(anilina) preparada quimicamente

AUTOR(ES)
DATA DE PUBLICAÇÃO

1991

RESUMO

Poly(aniline), PANI, is known since the last century. It is one of the most stable and attractive conducting polymers. PANI is generally prepared by oxidation of aniline in acid medium, using a chemical oxidant or by electrochemical oxidation. For technological purposes and large scale synthesis the chemical method is more adequate. As a consequence, in this work we studied in detail the chemical synthesis of PANI and compared the properties of the products with these of the electrochemically synthesized materiaI. We also studied the electrochromic properties of the chemically prepared PANI. PANI was obtained as a fine powder by the chemical oxidation of aniline in acid medium using three different oxidation agents: (NH4)2S2O8, KIO3 and K2Cr2O7. We studied the variation of the polymer conductivity as a function of the oxidation agent to monomer ratio, during the synthesis. The most conductive polymer was obtained in an excess of monomer. Using cyclic voltammetry experiments we compared the electroativity of these samples with an electrochemically prepared polymer. These experiments showed that the chemically prepared PANI has properties very similar to electrochemically prepared polymer. We also concluded that the oxidizing agent in the chemical synthesis does not influence these properties. The study of the effect of different electrolytes on the redox behavior of chemical PANI has showed that the electroativity is influenced by the nature of the anion in solution. Fine PANI films were deposited on optically transparent electrode by casting of a THF solution of chemical PANI. The electrochromic properties of these films were studied by chronoamperometry. These have showed that chemical PANI has a high chromatic contrast, good reversibility and can be switched for many redox cycles with good stability. Composites of PANI and cellulose acetate have been prepared by casting of films from a suspension of PANI in cellulose acetate solution. Its conductivity, measured as a function of PANI content, changes from 10 a 10 S.cm for 29 to 42% of PANI. A percolation behavior is observed.

ASSUNTO(S)

quimica organica - sintese polimeros e polimerização

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