Template-free Synthesis And Properties Of Polyaniline Nanostructures

The research on conducting polymers micro/nanostructures has become one of the most important fields in material science, in which, Polyaniline (PANI) has received great research interest because of its high conductivity, excellent environmental stability, simple synthesis, and controllable chemical/physical properties. In this work, we report on nanostructures and properties of conducting polyaniline synthesized by a template-free self-assembly method. The main results are summarized as follows:PANI doped with different dopants (APS, FeCl3, Fe(NO3)3 and Fe2(SO4)3) were obtained by the simplified template-free method, in which, APS, FeCl3, Fe(NO3)3 and Fe2(SO4)3 functioned as both oxidant and dopant. By changing synthesis conditions, it is found that there are three main factors which influence nanostructures of doped PANI. The first is the density of aniline monomer and oxidant; the second is molar ratio of aniline to oxidant; the third is varieties of oxidant and their redox potential. The room-temperature conductivity of the doped PANI ranges about from 10-2 S/cm to 100 S/cm. The temperature dependence of electrical conductivity of the doped PANI nanostructures shows a semiconductor behavior, and can be described by the three-dimensional Mott variable range hopping model. In addition, the measurements of water contact angles indicate that the PANI nanostructures exhibit hydrophilic behavior.PANI/TPA-BTD-BN nanowires were synthesized by the template-free method with a novel fluorescent substance TPA-BTD-BN as dopant and FeCl3 as oxidant. The average diameters of PANI/TPA-BTD-BN nanowires are about 100 nm. PANI/TPA-BTD-BN nanowires represent typical infrared absorption of PANI nanofibers. Fluorescence spectum of PANI/TPA-BTD-BN exhibits that PANI doped with TPA-BTD-BN have fluorescent character. With the increase of TPA-BTD-BN, the intensity of fluorescence emission peaks become greater. The room-temperature conductivity of PANI/TPA-BTD-BN ranges about from 10-1 S/cm to 100 S/cm, and the measurements of water contact angles show PANI/TPA-BTD-BN is hydrophilic.The effect of water, ethanol or HNO3 solution on resistance response of PANI-CSA films under atmospheric conditions was studied, in which, PANI-CSA was PANI doped with camphor sulfonic acid (CSA) by a "doping-dedoping-redoping" method. A lower amount of water molecules infiltrating PANI-CSA film can decrease the film's resistance possibly due to the enhancement of charge carrier transfer between polymer chains, whereas excessive water molecules can swell the inter-chain distance and result in the resistance increase quickly. Ethanol infiltrating PANI-CSA film can make the resistance increase and become much larger than the original value. However, HNO3 solution can decrease the film's resistance sharply possibly owing to doping effect of protonic acid and ionic conduction. These properties of PANI films can be applied to making chemical sensors.