Dopant, organic acids

Doping with fimcdonal dopants the properties of the ICPs, such as solubility in organic solvent [86] or water [87-91], can be modified by doping with appropriate dopant Camphorsulfonic acid is one of such dopants. CSA-doped PANI can be dissolved in m-cresol. A number of researchers [30, 60, 62, 64] blended... 

On comparing these results we find that in a sulphuric acid medium the peak potential of the PAn film corresponding to I and II anodic peaks lies between 0.09 and 0.625 V versus SCE, whereas the corresponding peak potentials in organic acids lie at higher potentials. The shift in peak potential has been attributed due to an interaction of the bulky dopant with the chemically flexible -NH- of the polymer [12]. 

The electronic spectra of 25% organic acid-doped PAn solution in DMSO has been reported to have absorption bands at 317, 449 and 646 nm, whereas at 50% doping the absorption bands are at 362, 420 and 832 nm, and for a neutral solution bands at 319 and 611 nm have been reported (Table 12.12). These observations have been ascribed to solute solvent interactions mediated by a functionalized dopant to give a ternary system. 

Organic Acids, Sulfonic Acids and Propionic Acid. The electrical conductivity of PDDT is about four to five orders of magnitude lower than in the case of iodine, but the electrical conductivity of the films is environmentally more stable. In addition, the dopant 4-dodecylbenzenesulfonic acid can act as a plasticizer for the PT film [273]. 1-Naphthalenesulfonic, ethylenebenzenesulfonic, methyl-ethylsulfonic, butanesulfonic, and pentafluoropropionic acids can be used for doping of POT and PDT [189]. 

The relative stabilities of the oxidized oligo(thiophene)s and PTs depend on the oxidation state (i.e. the doping level) [177, 541]. The dependence is weakest for FeCla-doped PAT above 10 Scm Below that value the dedoping rate decreases with decreasing electrical conductivity, as is the case for organic acid anions. For the dopant I2 and the dopant anion PFg the decay rate is proportional to the electrical conductivity [189]. The deterioration of the electrical conductivity with time depending on the doping level is also found for PAT with n = 12 [542]. PBT in the neutral (dedoped) form is stable up to 300 °C and... 

The incorporation of electrically conductive polymers (doped conjugated polymers) into non-conductive polymers to impart electrical conductivity has been demonstrated in a number of examples. Conjugated polymers shown below are generally non-conductive (semiconductive), but exhibit electrical conductivities often in excess of 1 S/cm with acid dopants, such as mineral acids (e.g., HCl, H2SO4), iodine, or organic acids such as dodecyl benzene sulfonic acid. 

For organic solvent solubility, an alternative approach to solubilising polyanilines and polypyrroles, without sacrificing high electrical conductivity, is the use of surfactant-like dopant anions. With polypyrrole this has recently been achieved via oxidation of the pyrrole monomer with ammonium persulfate in the presence of dodecylbenzene sulfonate [128,129]. Similarly, the conducting emeraldine salt form of PAn.HA can be readily solubilised in a range of organic solvents via the use of camphorsulfonic acid or dodecylbenzenesulfonic acid as the dopant, HA [130,131]. 

An important breakthrough in PPy chemistry was the discovery by Lee and coworkers95 in 1995 of a chemical polymerization route to an unsubstituted PPy that was soluble in organic solvents. They exploited the surfactant-like qualities of added dodecylbenzenesulfonate (DBSA 9) as a dopant anion to solubilize PPy formed during oxidation of pyrrole by aqueous (Nn4)2S208. The PPy/DBSA product, isolated as a black powder in 42% yield after 40 h reaction at 0°C, was very soluble in m-cresol, and could be dissolved in weakly polar solvents such as chloroform and dichloro-methane by the addition of an equimolar amount of dodecylbenzenesulfonic acid. A film cast from chloroform solution exhibited an electrical conductivity of 5 S cm-1, and its UV-visible spectrum was similar to that of electrochemically deposited PPy. 

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