Author(s):
Ferreira, Andr?? Andrade
Date: 2017
Origin: Oasisbr
Subject(s): Polianilina; Polimeriza????o qu??mica; Polimeriza????o interfacial; Condutividade el??trica; ENGENHARIAS: ENGENHARIA DE MATERIAIS E METALURGICA; Polianilina; Polianilina; Polimeriza????o qu??mica; Polimeriza????o qu??mica; Polimeriza????o interfacial; Polimeriza????o interfacial; Condutividade el??trica; Condutividade el??trica; ENGENHARIAS: ENGENHARIA DE MATERIAIS E METALURGICA; ENGENHARIAS: ENGENHARIA DE MATERIAIS E METALURGICA
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CAPES - Coordena????o de Aperfei??oamento de Pessoal de N??vel Superior
The aim of this paper is to analyze the structure and morphology of Polyaniline Emeraldine-salt form (PANI-ES) by conventional (PANI-ES/C1 and PANI-ES/C2) and interfacial (PANI-ES/I1 and PANI/ES/I2) polymerization using HCl 1M and 2M. The X-ray diffraction patterns (XRD) of PANI-ES/I1 and PANI-ES/I2 have presented higher crystallinity. Furthermore, the peak located at 2?? = 18.3?? has not been reported in scientific literature. PANI???ES/C1 and PANI???ES/C2 presented closed crystallinity percentage around 50 (?? 2) %, while PANI???ES/I1 and PANI-ES/I2 presented, respectively, 55 (?? 2) % and 63 (?? 2) % of crystallinity. PANI???ES/C1 showed cell parameters similar to those reported in literature. However, PANI???ES/C2, PANI???ES/I1 and PANI???ES/I2 have presented larger ???b??? unit cell parameter, from 8.9021 ?? (PANI???ES/C1) to ~16.2931 ??, due to the more efficient doping of the chloride ions. Fourier-transform Infrared Spectroscopy technique (FTIR) was useful to evaluate significant changes in the quinoid (Q) and benzenoid (B) bands: PANI-ES/C1 and PANI-ES/C2 presented the ratio Q/B, respectively, 0.4 and 0.6, indicating that the doping level by exposure to a higher dopant concentration has increased. An even more intense dopant action was verified in PANI-ES/I1 and PANI-ES/I2, presenting Q/B ratios of 0.7 and 0.9, respectively. These results reveal the more efficient doping level provided by the interfacial polymerization. Scanning Electron Microscopy (SEM) images showed that PANI-ES/C1 presented short nanofibers, while PANI-ES/C2 showed nanofibers length and diameter, respectively, around 61% and 13% higher than those found in PANI-ES/C1. However, PANI-ES/I1 and PANI-ES/I2 presented four different types of morphologies (nanoplates, nanorods, nanofibers and nanoflowers) due to the peculiarity of this polymerization method as well as to the lower dopant concentration. The difference of length and diameter between PANI-ES/C1 and PANI-ES/I2 nanofibers reaches 64% and 52%, respectively. Thermogravimetric Analysis (TGA) showed that the event related to the dopant release occurred for PANI-ES/I1 and PANI-ES/I2 in higher temperatures and larger temperature range, suggesting larger amount of dopant and better doping level. In addition, PANI-ES/C1 was the lesser stable sample, while the more stable sample was PANI-ES/I2. The PANI-ES/C1 presented the lowest electrical conductivity, 0.48 x 10-4 S.cm-1. Thus, PANI-ES/C2, PANI-ES/I1 and PANI-ES/I2 have presented, respectively, electrical conductivity values around 0.75 x 10-4 S.cm-1, 0.90 x 10-4 S.cm-1 and 1.20 x 10-4 S.cm-1. Furthermore, the interfacial polymerization methodology may favored higher electrical conductivity due to the better charge transport along the larger nanofibers.
O objetivo deste trabalho ?? analisar estrutura e morfologia de polianilinas na forma Sal de Esmeraldina (PANI-ES) obtidas por s??ntese convencional (PANI-ES/C1 e PANI-ES/C2) e interfacial (PANI-ES/I1 e PANI-ES/I2) usando 1 e 2M de HCl. Os padr??es de difra????o de raios X (DRX) das PANI-ES/I1 e PANI-ES/I2 apresentaram maiores cristalinidades (55 ?? 2 e 63 ?? 2%) enquanto PANI-ES/C1 e PANI-ES/C2 apresentaram cristalinidade em torno de 50 ?? 2%. PANI-ES/C1 apresentou par??metros de cela unit??ria semelhantes aos relatados na literatura. No entanto, PANI-ES/C2, PANI-ES/I1 e PANI-ES/I2 apresentaram maior valor do par??metro de c??lula unit??ria ???b???, que passou de 8.9021 para 16.2931 ??, devido ?? dopagem mais eficiente pelos ??ons cloreto. A t??cnica de Infravermelho com Transformada de Fourier (FTIR) foi ??til para avaliar as altera????es nas bandas quin??ide (Q) e benzen??ide (B): PANI-ES/C1 e PANI-ES/C2 apresentaram a raz??o Q/B = 0,6, indicando que o n??vel de dopagem por exposi????o a uma concentra????o de dopante mais elevada aumentou. Verificou-se uma a????o dopante ainda mais intensa em PANI-ES/I1 e PANI-ES/I2 apresentando raz??es Q/B de 0,7 e 0,9, respectivamente. Estes resultados revelam o n??vel de dopagem mais eficiente proporcionado pela polimeriza????o interfacial. As imagens de Microscopia Eletr??nica de Varredura (MEV) mostraram que PANI-ES/C1 apresentou nanofibras curtas, enquanto que PANI-ES/C2 apresentou comprimento e di??metro de nanofibras respectivamente, cerca de 61 e 13% superiores aos encontrados para a PANI-ES/C1. No entanto, PANI-ES/I1 e PANI-ES/I2 apresentaram quatro tipos diferentes morfologias (nanoplacas, nanobast??es, nanofibras e nanoflores) devido ?? peculiaridade deste m??todo de polimeriza????o. A diferen??a de comprimento e di??metro entre as nanofibras de PANI-ES/C1e PANI-ES/I2 atingiu 64 e 52%, respectivamente. A an??lise termogravim??trica (TGA) mostrou que o evento relacionado ?? libera????o de dopante ocorreu para PANI-ES/I1 e PANI-ES/I2 em temperaturas mais elevadas e maior faixa de temperatura, sugerindo maior quantidade de dopante e melhor n??vel de dopagem. Al??m disso, PANI-ES/C1e foi a amostra menos est??vel, enquanto que a amostra mais est??vel foi PANI-ES/I2. A PANI-ES/C1 apresentou a menor condutividade el??trica, 0,48 x 10-4 S.cm-1. PANI-ES/C2, PANI-ES/I1 e PANI-ES/I2 apresentaram, respectivamente, valores de condutividade el??trica em torno de 0,75 x 10-4 S.cm-1, 0,90 x 10-4 S.cm-1 e 1,20 x 10-4 S.cm-1, as quais podem ter sido favorecidas pelo m??todo de polimeriza????o devido ao melhor transporte de carga ao longo das nanofibras e tamb??m ??s diferentes morfologias.
