Polyaniline emeraldine base form

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 ... 

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... 

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. 

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. 

The Cu(II) complex with polyaniline (emeraldine base) exhibits a higher catalytic efficiency for the dehydrogenative oxidation of cinnamyl alcohol into cin-namaldehyde. Iron(III) chloride is similarly used instead of copper(II) chloride. The catalytic system is applicable to the decarboxylative dehydrogenation of man-delic acid to give benzaldehyde. The cooperative catalysis of polyaniline and cop-per(II) chloride operates to form a reversible redox cycle under oxygen atmosphere as shown in Scheme 3.4. The copper salt contributes to not only oxidation process but also metallic doping. The reduced phenylenediamine anionic species appear to be stabilized by the metallic dopants. 

Fig. 3. (a) Polyorthotoluidene (emeraldine base form) (b) sulfonated polyaniline (self-doped salt form). 

FIGURE 7.1 The oxidative polymerization of aniline in an acidic solution. The synthesized polyaniline forms in its doped emeraldine salt state that then can be dedoped by a base to its emeraldine base form. The bottom left scheme illustrates a typical reaction for making polyaniline. 

Since the polyaniline-CSA nanofibers have no absorption due to free CSA at 285 nm, CSA is most likely tightly incorporated as anions within the polyanOine backbone during the in situ polymerization of aniline in CSA solution. Dedoped polyaniline nanolibers (Figure 7.17a) can be obtained by dialyzing the pristine polyaniline-CSA complex against 0.1 M ammonium hydroxide, which produces the emeraldine base form of polyaniline. 

FIGURE 2.2 Change in the polymer backbone upon dedoping the emeraldine salt form of polyaniline to its neutral emeraldine base form. 

Jing, X., Y. Wang, and J. Qiang. 2004. Anti-corrosion property of emeraldine base form of polyaniline. Zhongguo Fushi Yu Fanghu Xuebao 24 (5) 301. 

Electrophilic substitution is a straightforward way to functionalize polyaniline. Substitution of sulfonic acid groups on the backbone of polyaniline, as shown in Figure 2.2, was first introduced by Epstein et al. [39] in the very first report of self-doped water soluble polyaniline. Their synthetic method involved the sulfonation of polyaniline using fuming sulfuric acid. The emeraldine base form of polyaniline (0.5 g) was dissolved in 40 mL of fuming sulfuric acid with constant stirring. 

Han et al. [64, 66] reported the synthesis of highly conductive and thermally stable self-doped mercaptopropanesulfonic-acid-substituted polyanilines by the concurrent reduction and substitution reaction between polyaniline and a nucleophile. These reactions were carried out on both electrochemically generated and free standing polyaniline films prepared from emeraldine base dissolved in N-methylpyrrolidinone. The electrochemically prepared films were dedoped with 5 % aqueous NaiCOs to convert them the into the emeraldine base form. The sulfonated polyaniline was prepared by reaction of a polyaniline emeraldine base film with 0.1 M 3-mercapto-l-propanesulfonic acid sodium salt in methanol under nitrogen at room temperature for approximately 14h [66]. A catalytic amount (0.01 M) of acetic acid was reported to accelerate the reaction. The resulting sulfonated polyaniline film was thoroughly rinsed with methanol, followed by 5 % aqueous NaiCOs to remove reactants. 

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