| Conductive polymer nano-composite micrespheres can effectively solve the poor processing performance, insoluble and refractory problems due to the rigid molecular structure and strong interaction between the molecular chains of the conductive polymers. In the same time make the two different nature ultra-fine particles together, composite particles in addition to a single ultra-fine particles’ surface effect volume effect and the quantum size effect, but also has a complex synergistic functional effects. Polyurethane is a class of both rubber elasticity and toughness and durability of metal exotic materials, but it is essentially a insulating material, its anti-static and poor conductivity limits its applications. Consider the molecular-level synergies and complementary effects of the composite material synthesized by polyurethane elastomer and conduvtive polymer. We prepared two kind of conductive composite nanospheres with core-shell structure by coating polyaniline and polypyrrole into the surface of waterborne polyurethane template. Our main results are listed as following:1. Appropriate choice of polyurethane structure, in order to synthesize the highly fragmented water-based polyurethane by emulsion polymerization. Water-based polyurethane is as a template, with polybinylpyrrolidone (PVP) as stabilizer, ammonium persulfate (APS) as initiator and hydrochloric acid as dopant, prepared polyurethane/polyaniline nanocomposite microspheres. Use laser light scattering particle size analyzer, field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric (TGA) to analyze the composite microspheres size, morphology, structure and thermal stability, respectively, and dual-electrode method to measure the electrical properties of materials. Studies have shown that water-based polyurethane and polyaniline nanocomposite microspheres with core-shell structure, and polyaniline shell thickness can be adjusted by the ratio of reactions. Polyurethane and polyaniline exists strong hydrogen bonds, thus ensuring the stability of nanocomposite microspheres. With aniline mass ratio of the reactants increased from10%to30%, the average size of nanocomposite microspheres increased from60nm to90nm, the conductivity increased from3.3×10-7Ω-1cm-1to5×10-5Ω-1cm-1, and also thermal stability was improved. In addition, nanocomposite microspheres with a higher solid content also had a better emulsion stability.2. Use the foregoing water-based polyurethane emulsion as a template, with PVP as a stabilizer, FeCl3·6H2O both as dopant and initiator, prepared polyurethane/polypyrrole nanocomposite microspheres by different shell thickness, respectively. And also the thickness of shell can be adjusted with the ratio of reactants. With pyrrole mass ratio of the reactants increased from10%to35%, the average size of nanocomposite microspheres increased from55nm to95nm, the conductivity increased from1.25×10-5Ω-1cm-1to7.74×10-4Ω-1cm-1, and also thermal stability was improved. Compared with polyurethane/polyaniline composite system, there are also strong hydrogen bonds, a shorter reaction time required and easier to select the reaction conditions, especially the conductivity of nanocomposite microspheres was increased obviously, and a higher emulsion stability in a similar mass ratio.3. We study the piezoelectric properties of foregoing two types of nanocomposite microspheres, and analysis the effects of its performance with different ratio, respectively. Observing the resistance of nanocomposite by different pressures and pression-decompression process, it is found that the conductivity was increased and the flexibility of composite system was decreased with increasing the content of conductive polymer. When the conductive polymer content of about30wt.%, the composite system is more sensitive to stress. But it is not easy to reply in a large pressure. The composite system can show good varistor properties in6KPa. In comparison, the repeatability of the polyurethane/polyaniline was better than polyurethane/polypyrrole.Composite materials synthesized by polyurethane elastomer and conductive polymer have molecular-level synergies and complementary effects on the structure. In particular, composite materials can be adjusted on the size, shape and composition. In addition, its molecular structure can be designed, conductivity can be adjusted and morphological characteristics can be controlled. So such nanocomposite microspheres are designable, in order to gain specific physical and chemical properties. It is expected as antistatic coatings, corrosion-resistant coating, absorbing coating, multi-sensor, electrochromic devices, electroluminescent devices, biomedical sensors and so on. Also it can be widely used in chemical, medicine, immunology, electronics industry, information industry, military and other fields. |
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