Polyaniline emeraldine production

Unsaturated heterocycles and aniline have been polymerized either chemically or electrochemically on electrode surfaces. The systems are attractive as they are often significantly more stable than PA under atmospheric conditions. The importance of quinoid vs. aromatic structure becomes apparent if the chemistry and conductivity of polyaniline fPANIl is examined. The initial emeraldine salt product of PANI is believed to have the following... 

Encapsulation chemistry similar to that described above (exchange of anilinium, followed by oxidation with peroxydisulfate) was foimd to produce polyaniline not only in zeolite Y, but also in montmorillonite clay. 5 Spectral features (UV-VIS, IR and EPR) of the products were indicative of emeraldine salt and base formation, respectively. The change in basal spacing of the montmorillonite upon intercalation provided additional evidence for the inclusion polymerization. 

Polyanilines (Scheme 36) are conjugated polymers whose it electrons are delocalized over the whole molecule. They are important conducting polymers that also act as semiconductors, in a similar manner to inorganic semiconductors121 m. They are made by chemical or electrochemical (anodic) oxidation of aniline. The product, a poor textile colorant, dates from the 1860s, and is still known by the name given at that time, emeraldine. In the electrochemical process, it is possible to produce thin films directly on conductive substrates. Polyanilines have been used in photoelectrochemical devices124-126. 

The synthesized produet was a powder by green color that indicates about production of the emeraldine form of polyaniline, exactly emeral-dine salt Vkn-HCl. The produced samples of PAn/nano-Ti02- S composites had more light tinctures their intensities were decreased with the increasing of the TiO content in the initial reaction mixture. 

Magnetic susceptibility and electron spin resonance data of self-doped sulfonated polyaniline shows the presence of Curie like susceptibility and temperature independent Pauli like susceptibility. The product of the spin susceptibility and temperature (xT) versus temperature for the emeraldine base sulfonated polyaniline is shown in Figure 2.30 [41]. Based on the Pauli spin concentration, the density of states at the Fermi level N( f) (from the slope) is 0.8 state/eV-two rings and an effective Curie spin concentration (from the T = 0 intercept) is 0.02 spin/two... 

Kinetic studies by Shim and Park [132] determined the autocatalytic rate for polyaniline growth. Other reaction kinetic studies and comparison of the properties of the chemically synthesized emeraldine to the electrochemical product led Mohilner et al. [131] to conclude that the oxidation of aniline occurs via a free radical mechanism that produces the emeraldine octamer as the primary product. Emeraldine is a blue-violet base form of polyaniline that forms dark green salts as described by Green and Woodhead [133]. Emeraldine loses two protons upon ox-... 

Ohsaka et al. [138] studied the oxidation of aniline in acidic, neutral, and basic solutions. Their polyaniline had a structure similar to that of the emeraldine and nigraniline forms that were previously reported [131]. They produced electroactive products using acidic electrolytes. These materials had conductivities ranging from 0.2 to 6 X 10 - S cm . 

A wide range of alkyl- and alkoxy-substituted polyanilines of the general types 6 and 7 have been synthesized by the chemical or electrochemical oxidation of appropriately substituted aniline monomers.41,i32-i3s Such substitution imparts solubility in organic solvents upon the emeraldine salt products that is markedly improved over the parent (unsubstituted) PAn.HA salts. The poly(2-methoxyaniline) (POMA) species, in particular, has been the subject of extensive studies. This species has the additional attractive feature of being soluble in water after being wet with acetone. 

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