Data/hora: 17/06/2024 02:31:26

Biblioteca(s): | Embrapa Instrumentação.
Data corrente: | 22/12/1999
Data da última atualização: | 01/03/2010
Autoria: | MATTOSO, L. H. C.; MACDIARMID, A. G.
Afiliação: | EMBRAPA-CNPDIA; University of Pennsylvania-Chemistry Department.
Título: | Polyanilines, oxidation states.
Ano de publicação: | 1996
Fonte/Imprenta: | In: SALAMONE, J.C. (Ed.). Polymeric materials encyclopedia. Boca Raton: CRC, 1996.
Páginas: | p. 5505-5513.
Idioma: | Inglês
Conteúdo: | First reports on the synthesis of aniline-based compounds are from the last century. Later polyaniline (PAni) was described as existing in four different oxidation states, each of which was an octamer. A few scattered papers appeared in the 1950s and 1960s on Pani oligomers and the electrochemical and FeCl3 oxidation of aniline. Until relatively, Pani, probably the oldest know synthetic organic polymer, consisted of an ill-defined class of materials obtained by the chemical or electrochemical oxidative polymerization of aniline. Early studies were fraught with problems of uncertain composition, and it was not until the mid-1980s the advent of better characterized materials that significant physical studies became possible. Polyanilines started to be extensively studies as conducting polymer after 1980, with several groups following suit during the following decade. The fascination of the conducting polymer community with this complex, challenging and potentially tecnologically important polymer system is due to its unique properties, in particular, ease of doping by protonic acids, stability in the doped and conductive state, solubility, and processability in the form of flexible high-strength films and fibers. Such characteristics have made PAni an outstanding conducting polymer with commercial viability in technological application such as rechargeable batteries, conductive coating on textiles, cable shielding, chemical sensors, electromagnetic shielding, electrical and electrochemical devices, and electrochromic displays. The term "polyaniline" as commonly employed, refers to a class of polymers of which the base form has the generalized composition and consists of alternating reduced (y), and oxidized (1-y), repeat units. (Structure !) In principle y can be varied continuosly from one, the completely reduced polymer, to zero to give the completely oxidized polymer (Structure 2 and 3). The terms leucoemeraldine, protoemeraldine, nigraniline, and pernigraniline, used in the following discussion will refer to the different oxidation states of the polymer where y=1, 0.75, 0.5, 0.25 and 0 respectively. These names apply to polymers either in the base form, such as emeraldine base or in the protonated salt form, such as emeraldine hydrochloride. Although, in principle, the oxidation staates can vary continuously, it will be shown that PAnis can exist in only three discrete oxidation states: leucoemeraldine, emeraldine and pernigraniline, the order oxidation states being a mixture of these. The imine nitrogen atoms in any of the species can be protonated in whole or in part to give the corresponding salts (doped form), the degree of protonation of the polymeric base depending on its oxidation state and on the pH of the aqueous acid. In this paper we present a brief review on the synthesis and doping of Panis in the various oxidation states and on the intercon version between the different oxidation states.
Palavras-Chave: | Polianilinas.
Categoria do assunto: | --
Registro original: | Embrapa Instrumentação (CNPDIA)
Exemplares: | CNPDIA - (5621-1) - UPC - SP - -- - PROCI-96.00132 -  - 1996.00132 - DIS