Synthesis And Characterization Of Polypyrrole Nano/microstructures

Polypyrrole (PPy) is one of the excellent conducting polymers with good environment stability and high conductivity, and it is easy to synthesis. Nano/microstructured polypyrrole possess the advantages of both nanostructures and organic conductors. They have potential applications in conducting molecular wires, chemical sensors (such as actuators), and gas-separation membranes. Here, PPy nanowires was successfully synthesized by chemical oxidative polymerization. In addition, Monodisperse core/shell latex particles composed of polystyrene (PS) core and a thin conductive PPy shell were synthesized by two-stage polymerization. A plausible mechanism for the formation of PPy nanowires and PS/PPy core/shell structures was discussed. The main results are concluded as follows:(1) Superhydrophilic PPy nanowires was synthesized at about 15℃by oxidative polymerization in the presence of cetyltrimethylammonium bromide (CTAB), and Phosphonic acid (PA) was used as the dopant. PPy nanowires are of the uniform diameter of 40-50 nm with length up to several micrometers. It is found that the presence of CTAB is the necessary condition to synthesis PPy nanowires, which could be synthesized in a wide concentration range of CTAB (from 0.0014 to 0.017 M). PA herein may assist CTAB by stabling the micelles of pyrrole and benefits the formation of well-defined PPy nanowires, while the concentration of PA ranges from 0 to 3M. Moreover, the concentration of pyrrole (range from 0.019-0.038 M) does not play an important role in forming the uniform nanowirs, but there are to be some ribbon-like PPy when the concentration decreases to 0.0048M. Furthermore, wires composed of PPy nanoparticles are formed at 50℃, while irregular PPy nanowires are formed at 0℃. Additionally, TGA curves show that the thermal stability of PPy nanostructure prepared with CTAB and PA is higher than that prepared without CTAB or PA, and the PPy nanowires prepared with CTAB and PA suffers only about 55% loss of its original weightwhen heated from room temperature to a temperature as high as 1000°C in nitrogen.(2) Wettibility controllable PPy nanowires was synthesized at about 15℃by oxidative polymerization in the presence of CTAB, where 2-acrylamido-2-methyl- -propanesulfonic acid (AMPSA)was used as the dopant. PPy nanowires are of the uniform diameter of 20-40 nm with length up to several micrometers. It is found that, compared with the PPy nanowires synthesized with PA used as the dopant, the system with AMPSA appears to be able to fit the concentration range of acid(from 0 to 0.034 M) and pyrrole(from 0.0048 to 0.038 M), while a more wide temperature range(from 0-15℃). Furthermore, the water CA increases from 41°to 99°with the change of HTAB/AMPSA ratios under a fixed monomer concentration. Additionally, the thermal stability of this PPys was also great improved with the increasing of the concentration of AMPSA (range from 0-0.04 M) and CTAB (range from 0-0.14 M).(3) Monodisperse core/shell particles composed of polystyrene (PS) core and a thin conductive PPy shell were synthesized by two-stage polymerization. It is found that PPy nanoparticles are packed densely and deposited onto the surface of micrometer-sized PS latex to form Monodisperse core-shell structure of PS/PPy particles. In addition, part of the PPy nanoparticles congregated together to form submicrometer-sized particles with increasing of the concentration of pyrrole.