Synthesis, Characterization Andelectric Beheviours Of PANi, PANi/T-ZnOw Composites

Polyanilme is the most promising candidation for electromagnetic absorption applications in its controllable electronic properties, as well as its ease of preparation and excellent environmental stability.In this thesis, the polyanilme were synthesized and in situ doped with HCl through the chemical oxidation polymerization. The structures of the synthesized samples were characterized by elemental analysis, Fourier Transform Infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The best conditions for synthesis of conducting polyanilme are as follows: the concentration of HCl is around of 1-2mol/l, the molar ratio of APS to Ani is about 1.2, the temperature is maintained in the range of 0～2℃and the reaction time is 6h.Thermal analysis showed that the emeraldme base had more stability than that of the HCl doped emeraldme salt. The conductivities and electromagnetic properties were studied by four-probe electric measurements, and the results indicated that the conductivities of polyanilme doped with HCl were 10°～10¹S/cm, while the un-doped samples were 10^-6～10^-5S/cm. The tests of the electromagnetic parameters of the samples were evaluated, and it was found that the dielectric loss appeared more effective than magnetic loss in the frequency range from 2 to 18GHz for the samples of HCl doped polyaniline. The microwave reflectivity for the conducting polyaniline in 6—18 GHz was -4 to -8dB when the coating thickness was 2.50mm.Through self-assembled monolayer technique, polyaniline was synthesized on the modified surface of the tetra-needle-like ZnO whisker (T-ZnOw), leading to a novel kind of core-shell structured composites.γ-Aminopropyltriethoxysilane (APTS) was used as coupling agent to form a dense aminopropylsilane monolayer on the surface of T-ZnOw, followed by chemical oxidative polymerization of aniline. The FT-IR spectra revealed that the T-ZnOw was successfully modified by APTS and the T-ZnOw/PANi core-shell structured composites finally formed. The SEM results showed that the T-ZnOw was coated with PANi layer completely and homogenously and its peculiar structure was almost intact. The thickness of the polyaniline shell can be controlled by the process and conditions. The electric conductivity of pellets pressed from the as-prepared composite was 6.2×10^-4 S/cm. Because of low conductivity, the PANi/T-ZnOw composites appeared bad effect for electromagnetic absorption.