Self-assembled polyaniline (PANI) nanotubes were prepared in the presence of three different sulfonic acids as dopant, namely, p-toluenesulfonic acid, camphorsulfonic acid, and tetrakis(4-sulfonatophenyl)porphyrin, by oxidative polymerization using ammonium peroxydisulfate as the oxidant. The morphology of the PANI nanotubes was determined by SEM and TEM and the electrical conductivity was measured as a function of temperature. The PANI nanotubes were also characterized by FTIR, XRD, UV-Vis, and cyclic voltammetry. We have found that the dopants had a noteworthy effect on the electrical conductivity whithout significant changes in the morphology of the PANI nanotubes. 1. Introduction Polyaniline is a prototype conducting polymer; it is particularly attractive for electronic applications due to its facile synthesis, environmental stability, unique electronic properties, and simple acid/base doping/dedoping chemistry [1]. In situ polymerization is one of the most important methods developed so far to incorporate the dopant in polyaniline during synthesis. A great variety of organic and inorganic dopant acids can be used, such as hydrochloric, sulfuric, nitric, phosphoric, perchloric, acetic, formic, tartaric, camphorsulfonic, methylsulfonic, ethylsulfonic, and 4-toluenesulfonic acid. The size and amount of dopants play an important role in influencing the morphology of conducting polymers. Recently, we have demonstrated that the morphology of sulfonated porphyrin doped polyaniline can be changed from one-dimensional nanotube to three-dimensional cauliflower structure by simply changing the volume ratio of dopant to aniline [2]. In our earlier reported work, we have prepared conducting fibrous polyaniline: nylon-6,6 by stirring aniline and nylon-6,6 solution with the help of magnetic bar, as in this technique the conductivity of the fibrous material depends on the ratio of conducting polymer present in fibrous material [3, 4]. Zhang et al. have demonstrated that the polymeric acid has significant effect on the morphology and size of the polyaniline nanotubes [5]. Many techniques have been used to synthesize PANI nanostructure such as stirring [6–8], static placement, [9] sonication [10–12], and emulsion polymerization [13–16]. Particularly, conducting polymer nanotubes and nanofibers have received growing interest in recent years due to their unique properties and promising potential applications in nanodevices [17–21]. The investigation of nanostructured conducting polymers has great importance for both scientific and technological points of view. In this
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