Polyanilines self-doping

Figures Schematic illustrations of (a) 50% sulfonated and (b) 100% sulfonated polyanilines (self-doped forms).

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

In addition to positively impacting issues of dedoping of pH and thermally sensitive polymers such as polyaniline, self-doped forms enable the combination of p- and n-type conducting polymers without their spontaneous discharging by the concerted recombination of carriers and counterions. This has resulted in the formation of conjugated polymer p/n junctions, not possible with standard conjugated polymers. ... 

Fig. 1. (a) Leucoemeraldine base (b) emeraldine base (c) pernigraniline base (d) polyCparaphenylene sulfide) le) emeraldine hydrochloride salt polymer (f) poly(orthotoluidine) (emeraldine base form) (g) sulfonated polyaniline (self-doped salt form). 

Polyaniline (PANI) can be formed by electrochemical oxidation of aniline in aqueous acid, or by polymerization of aniline using an aqueous solution of ammonium thiosulfate and hydrochloric acid. This polymer is finding increasing use as a "transparent electrode" in semiconducting devices. To improve processibiHty, a large number of substituted polyanilines have been prepared. The sulfonated form of PANI is water soluble, and can be prepared by treatment of PANI with fuming sulfuric acid (31). A variety of other soluble substituted AJ-alkylsulfonic acid self-doped derivatives have been synthesized that possess moderate conductivity and allow facile preparation of spincoated thin films (32). 

Figure 13. (a) Substituted polypyrrole, (b) self-doped polypyrrole, (c) heteroaromatic polymer showing the monomer unit, (d) composite polypyrrole-polyelectrolyte, and (e) hybrid material. (Polyaniline macroion photo supplied by Gomez-Romero and M. Lira.)... 

Jung JW, Lee JU, Jo WH (2009) High-efficiency polymer solar cells with water-soluble and self-doped conducting polyaniline graft copolymer as hole transport layer. J Phys Chem C 114 633... 

Title Method of Making Novel Water-Soluble and Self-doped Polyaniline Graft Copolymers... 

Polyaniline has been grafted onto the poly(styrenesulfonic acid-co-aminostyrene) backbone using aniline, ammonium persulfate, and hydrochloric acid. The graft copolymer is water soluble and self-doping and can be used in electrical and marine anticorrosive applications. 

Preparation of Self-doped Polyaniline Graft Copolymer... 

The synthesis of self-doped conducting polyaniline was achieved by sulfonation of the aromatic units with fuming sulfuric acid. The sulfonated polyaniline has a conductivity of 0.1 S/cm, which is independent of pH [191]. 

Fig. 3.10. Some of the more commonly encountered organic conductor materials (a) polypyrrole, (b) polyaniline, and (c) poly(3,4-ethylenedioxythiophene) (PEDOT). When combined with water soluble organic acids (e.g. sulfonic acids like benzosul-fonic acid) many of these polymers can form doped complexes which are highly conductive and can be dispersed into suspension. Substituted versions of these polymers which are self-doped have also been developed.

The various ring-substituted PANI systems include one that embodies the concept of self-doping sulphonated polyaniline (SPAN). In SPAN, about half the number of phenyl rings of emeraldine salt arc monosubstituted with an — SOj" group (Yue et al. [327]). This polymer is x-ray amorphous, as is its de-protonated, non-conductive salt form obtained upon dissolution of... 

The comparative XPS studies was done on the thermal stability of polyaniline salts doped in three different ways such as (i) heavily protonated by HCIO4 or metanilic acid (ii) self-doped by sulphonation of emeraldine base and (iii) co-polymerizing aniline with metanilic acid to give a self-doped material which was fitrther protonated by HCIO4 or metanilic acid. Polyaniline protonated with HCIO4 underwent de-protonation on thermal or water treatment easily whereas the polyaniline with SO," groups attached by covalent bonds showed the lowest stability [169]. 

As the degradation of polyaniline occurs via an imine intermediate [281,284], Kim et al. [285] prepared self-doped polymer by alkylsulphonate substitution in the polymer backbone, Besides self-doping for a facile redox process, the perceived advantage of this bulky substituent includes the protection of nitrogen centres from nucleophiles responsible for irreversible degradation of polyaniline. Poly(aniline N-butylsulphonate) retained its reversible electrochromic response up to 150 000 cycles when scanned between its oxidized and reduced states (between 0.2 and 0.5 V) then started diminishing slowly. The excellent redox cyclability of poly(aniline N-butylsulphonate) over unsubstituted polyaniline was also confirmed by chronoabsorptom-etry by Kim et al. [285],... 

A major advance in the solubilization of polyaniline was self-doping by the attachment of a sulfonic acid side group to the backbone ring [47,48]. The resulting material is essentially a polyzwitterion with the acid proton transferring to the basic amine backbone. The polymer is then soluble in mildly basic aqueous solutions and can be coated over large areas. 

C. Cheng, J. Jiang, R. Tang, and F. Xi, Polyaniline nanostructures doped with mono-sulfonated dendrons via a self-assemhly process, Synth. Met., 145, 61-65 (2004). 

C. Zhang, G. Li, and H. Peng, Large-scale synthesis of self-doped polyaniline nanofibers. Mater. Lett., 63, 592-594 (2009). 

H. R. Ghenaatian, M. F. Mousavi, S. H. Kazemi, and M. Shamsipur, Electrochemical investigations of self-doped polyaniline nanofibers as a new electroactive material for high performance redox supercapacitor, Synth. Met., 159, 1717-1722 (2009). 

N. J. Pinto, P. L. Carrion, A. M. Ayala, and M. Oitiz-Marciales, Temperature depeudeuce of the resistance of self-assembled polyaniline nanotubes doped with 2-acrylamido-2-methyl-l-propanesulfouic acid, Synth. Met., 148, 271 274 (2005). 

R.-H. Lee, H.-H. Lai, J.-J. Wang, R.-J. Jeng, and J.-J. Lin, Self-doping effects on the morphology, electrochemical and conductivity properties of self-assembled polyanilines. Thin Solid Films, 517, 500-505 (2008). 

G. Li, C. Zhang, H. Peng, K. Chen, and Z. Zhang, Hollow self-doped polyaniline micro/ nanostructures Microspheres, aligned pearls, and nanotubes, Macromol. Rapid Common., 29, 1954-1958 (2008). 

Y. Ma, S.R. Ali, L. Wang, P.L. Chiu, R. Mendelsohn, and H. He, In situ fabrication of a water-soluble, self-doped polyaniline nanocomposite the unique role of DNA functionalized single-walled carbon nanotubes, J. Am. Chem. Soc., 128, 12064—12065 (2006). 

Nguyen M. T. and Diaz A. F., Synthesis of new water-soluble self-doped polyaniline. Macromolecules, 1995,28,3411. 

Yamamoto K. and Taneichi D., Electrochemical catal3d ic reduction of oxygen by a self-doped polyaniline-co-porphyrin complex-modified glassy carbon electrade, Macromol Chem. Phys., 2000,201,6-11. 

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