Polyanilines base forms

Chen, C.H., 2003. Thermal and morphological studies of chemically prepared emeraldine-base form polyaniline powder. Journal of Applied Polymer Science 89, 2142—2148. 

The experimental UPS spectra of the emeraldine base form of polyaniline is compared with VEH-derived DOVS in Figure 5-18 97. The DOVS were derived from the VEH band structure calculations shown at the bottom of Figure 5-18. 

The emeraldine base form of polyaniline may also react in non-aqueous electrolytes, such as a LiClOl -propylene carbonate solution, with the formation of the conductive emeraldine hydroperchlorate salt ... 

Sample Preparation. Chemically polymerized 2-ethyl polyaniline, with reported molecular weight of 5000, was prepared by the method outlined by Leclerc et al. (15). Treatment of the insoluble product with ammonium hydroxide solution resulted in transforming the salt into the soluble EB form, which exhibited slight solubility in methanol. The soluble EB form of PANi is known to be readily protonated under acidic conditions, producing the highly insoluble ammonium salt form (16.17). In order to maintain the free amine base form in solution, it was necessary to synthesize the silica gel in the presence of a minimal amount of acid catalyst. 

Polyaniline is structurally much more complicated than PA, even if we restrict our attention to the emeraldine base (EB) and salt (ES) forms. There are two classes of base forms, to which correspond two classes of salt forms ESI and II [28], and the EB - ES interconversion does not mix the classes. This interconversion corresponds to addition or removal of a proton onto the N atom in the chain without changing the total number of electrons this causes a conductivity change by more than 10 orders of magnitude, from 10-10 S/cm to > 1 S/cm [52]. 

Polyaniline provides the prototypical example of a chemically distinct doping mechanism [33,34], Protonation by acid-base chemistry leads to an internal redox reaction and the conversion from semiconductor (the emeraldine base) to metal (the emeraldine salt). The doping mechanism is shown schematically in Fig. II-2. The chemical structure of the semiconducting emeraldine base form of polyaniline is that of an alternating copolymer, denoted as [(1A)(2A)] , with... 

Conducting polymer blends based upon polyaniline (PANI) are a new class of materials in which the percolation threshold for the onset of electrical conductivity can be reduced to volume fractions well below that required for classical percolation (16% by volume for globular conducting objects dispersed in an insulating matrix in three dimensions) [277,278], The origin of this remarkably low threshold for the onset of electrical conductivity is the self-assembled network morphology of the PANI poly blends, which forms during the course of liquid-liquid phase separation [61],... 

This material can also be formed upon "doping" the corresponding emeraldine base form of polyaniline with aqueous HCl, resulting in a large increase of the number of unpaired spins,probably as diaminobenzene radical cations.55 The similarity of the electronic properties of protonated phenyl... 

Alternative oxidants such as potassium iodate were also explored for the intrazeolite polymerization of aniline in NaY and acidic forms of Y zeolite. With peroxydisulfate, the polymerization proceeded only if a sufficient supply of intrazeolite protons was available. No polymer formed in either NaY or in acid zeolites with neutral iodate solution, but at low pH polyaniline was obtained in all hosts. The open nature of the zeolite host, even when partially filled with polymer, permits the introduction of base (such as ammonia). On admission of ammonia into the emeraldine salt-containing zeolite, the protonated polymer was converted into the neutral emeraldine base form. 

The polyaniline can be converted to the base form by stirring with a solution of aqueous ammonia (3%) for 3 h followed by washing as in step 3. 

BEDT-TTE]2Br-3H2O phases, respectively. Similarly, a hybrid material based on polyaniline including 50% w/w of Cs[In(dmit)2] was recently isolated and shows a conductivity of 2.3 x 10" S This hybrid material is formed as a flexible, self-supporting film. A different method was applied by da Cruz et al. to prepare such hybrid films. Pyrrole is electropolymerised in acetonitrile using the inorganic... 

Compared to block copolymers, there have been relatively fewer examples of using homopolymers for nanofabrication. Nevertheless, some polymers with amphiphilic properties were also used in the fabrication of nanostructures with various metal salts/complexes. For example, polyaniline (PANI) emeraldine base formed self-organized mesomorphic structures when mixed with Zn(DBS)2 by the coordination between Zn2+ and the imine nitrogen atoms on the polymer main chain.100 The resulting supramolecule PANI[Zn(DBS)2]0.5 had a comb-shaped... 

By the mid-80s it was clear to most researchers that success on the conductivity side had taken its toll on polymer processability. Attention turned back to restoring the solubility and mechanical properties of the polymer. Polyaniline received the most attention initially. The nonconductive emeraldine base form is soluble in A-methylpyrrolidone [28] and films can be cast. Subsequent doping with a protonic acid from aqueous solution, or in situ with a photo-acid generator [45], is necessary to achieve conductivity. Polyaniline is also soluble in sulfuric acid, not the most convenient of solvents. Nevertheless it proved possible to spin fibers [46], cast films and extmde sheets of conductive polyaniline sulfate, but the laboratory experiments did not make the transition into large-scale manufacmring. 

M. Cochet, G. Louarn, S. Quillard, M. I. Boyer, J.P. Buisson, and S. Lefrant, Theoretical and experimental vibrational study of polyaniline in base forms non-planar analysis. Part L... 

In this paper, we have investigated the electronic structure of different base forms of polyaniline by using X-ray photoelectron spectroscopy. The protonated emeraldine form has been also investigated to determine the charge delocalization along the chain as a function of the pH. 

In a first step, the electronic structure of the polyaniline base form has been followed versus the oxidation state. After that, we have proceeded further with the protonated emeraldine form. In all cases, the binding energy scale has been calibrated by setting the Cls core level main peak at 284.4 eV. 

Fig. 2. Evolution of the XPS Cls core level spectra of the polyaniline base form as a function of the oxidation state.

The term "polyaniline", as commonly employed today2,3 refers to a class of polymers consisting of up to 1,000 or more (ring-N-) repeat units, which can be considered as being derived from a polymer, the base form of which has the generalized composition and con-... 

It has recently been observed31 that the completely reduced base form of polyaniline, (leucoemeraldine), spontaneously reduces, and is itself oxidized, when its solution in NMP is mixed with an NMP solution of the completely oxidized base form of polyaniline, (pernigraniline). This reaction may be studied by "titrating" a solution of the leucoemeraldine with a solution of pernigraniline and by following the course of the reaction by the changes in the electronic spectrum of the reaction mixture. When equimolar solutions of the reactants are mixed this redox reaction is found to approach equilibrium after 20 hours at room temperature, to produce the emeraldine base, viz.,... 

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