Hydrochloric acid doped polyaniline

As mentioned in the introduction, the electrical conductivity upon doping is one of the most important physical properties of conjugated polymers. The conductivity ranges from lOOOOOS/cm for iodine-doped polyacetylene [41], 1000 S/cm for doped and stretched polypyrrole [42], to 500 S/cm for doped PPP [43], 150 S/cm for hydrochloric acid doped and stretched polyaniline [44], and 100 S/cm for sulfuric acid doped PPV [45] to 50 S/cm for iodine-doped poly thiophene [46]. The above listed conductivities refer to the unsubstituted polymers other substitution patterns can lead to different film morphologies and thus to a different electrical conductivity for the same class of conjugated polymer in the doped state. 

Hydrochloric acid as well as camphor sulfonic acid doped polyaniline prepared in chloroform often have [59] log a proportional to T as expected for quasi-one-dimensional variable range hopping, Equations (3) and (4). Generally, the higher conductivity samples have a weaker temperature dependence at low temperatures (Tq 700-1000 K for T<80 K), and lower conductivity samples a stronger temperature dependence (To 4000 K). The smaller Tq for the more highly conducting samples has been associated with weaker localization due to improved intrachain and interchain order. 

Hydrochloric acid as well as camphor sulfonic acid doped polyaniline prepared in chloroform often have log a proportional to as expected for quasi-one-dimensional variable range hopping (VRH), Fig. 46.11, [73,121,143] ... 

Authors [9-14] have reported an X-ray diffraction pattern for organic acid-doped polyaniline which is almost same as that of H2S04-doped polyaniline. Organic acid-doped polyaniline has been shown to have a better thermal stability than hydrochloric acid-or sulphuric acid-doped polyaniline. 

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). 

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. 

The base polymer was then doped by dipping the sample into a dilute aqueous hydrochloric acid solution. As this particular conducting salt is insoluble, the resist (a typical diazonaphthoquinone-novolac formulation [4] could be directly coated on top of the polyaniline without any interfacial problems. 

Polyaniline Doped With Hydrochloric Acid. "Emeraldine Hydrochio ide ... 

Common protonic acids such as hydrochloric and sulfuric acids leave the polymer highly polar. Dopants with long polymer chains such as dodecylbenzenesulfonic acid can lessen the polar character and change the interactions of the polymer [7,15]. The effect is clearly evident from the solubility/dispersibility of polyaniline doped with dodecylbenzenesulfonic acid in nonpolar solvents such as toluene and xylene [7,16]. Certain functionalized protonic acid solutes such as camphorsulfonic acid have been shown to be highly effective in rendering the doped polymer soluble in polar organic solvents such as m-cresol [7]. 

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