Preparation And Electrorheological Properties Of Polyaniline-based Nanocomposites

Electrorheological(ER)fluid is a kind of intelligent material.It is a general term for a class of fluids prepared by dispersing polarizable solid particles into an insulating medium(silicone oil,mineral oil,etc.),and its rheological properties can be controlled by an electric field.The solid particles dispersed in the ER suspension will polarize and form a chain structure along the field direction by the applied electric field.Therefore,they exhibit a phase change from a liquid to a solid.In this fast and reversible process,the rheological properties of the ER fluid have a significant change.Conductive polymers having a ?-conjugated structure have been used as ER materials,among which polyaniline is one of the most commonly used ER materials due to its excellent thermal stability and chemical stability,ease of synthesis,its price is relatively low,and its conductivity can be adjusted by doping-de-doping or compounding.Polyaniline has been widely used as an ER fluid,and its morphology has a crucial influence on its performance.Therefore,polyaniline with special morphology has been the focus of research.At present,PANI with the shape of fiber-like,rods-like and spherical nanoparticles have been prepared,which enhance its polarizability and rheological properties.Therefore,we designed and prepared polyaniline with special morphology and a high-performance polyaniline composite by utilizing the properties of polyaniline.The following are the main experimental contents:(1)We fabricated a clip-like polyaniline(PANI)nanofiber by using an insitu chemical oxidative polymerization assisted with a surfactant mixed system.First of all,three kinds of surfactants(cetyltrimethyl ammonium bromide(CTAB),polyvinyl pyrrolidone(PVP),sodium dodecyl benzene sulfonate(SDBS))were used to provide different mixing combination.The combination of different surfactants has an important role on the morphology of obtained PANI nanoparticles.We propose possible synthetic mechanisms which CTAB and PVP as a structure directing agent plays the role of template to adjust the morphology.(2)A novel core–shell-type electrorheological(ER)composite material was fabricated via using polyaniline as insulating layer to the outer surface of the core conductive metal-organic framework compound(MIL-125)of controlled size and morphology.MIL-125 was firstly synthesized by a solvothermal method,and then polyaniline was synthesized in a polar solvent and a tight coating was successfully achieved.This core-shell structure greatly enhances the polarization of dispersed particles,thereby improving their rheological properties.(3)By improving the surface of carbon nanotubes to have an aniline group and then using it as the core conductive layer,a layer of polyaniline was synthesized on the outer surface of CNTs by in-situ oxidative polymerization,and its morphology and possible synthesis mechanism were analyzed.A new composite material,CNT@PANI,was prepared.The conductivity is reduced by a dedoping process and make it become an excellent electrorheological material.The morphology of the above materials was characterized by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The structure was characterized by X-ray powder diffraction,Fourier-transform infrared spectroscopy(FTIR)and thermogravimetric analyzer(TGA).In addition,the rheological behavior of the electrorheological fluid prepared from the above materials was characterized by a rotational rheometer by dispersing the particles into silicone oil and their dielectric properties were analyzed by dielectric spectroscopy.The results show that the electrorheological fluid prepared from the above materials have high ER properties.