Preparation Of Polystyrene / Silver Core - Shell Microspheres And Its Application In Dielectric Elastomers

Conductive polymer microspheres were prepared by using polymer microspheres as templates and using metals as cladding layers. It had advantages:the round appearances and controllable uniform sizes and light qualities of polymer microspheres, good electrical properties of metals. Thus composite conductive microspheres had a wide range of applications. Polystyrene/Ag composite microspheres were prepared in this article, then they were used as templates to prepare dielectric microspheres. The dielectric microspheres were used to study dielectric elastomers of silicone rubbers. The main contents of this paper are as follows.(1) The synthesis of P(St-AA)/Ag composite microspheres. Carboxyl polystyrene microspheres (P(St-AA)) were synthesized by copolymerization of the propylene and acrylic acid monomers. The carboxyl groups of P(St-AA) microspheres were negatively charged in liquid, so [Ag(NH3)2]+ions could be bounded on the surfaces of P(St-AA) microspheres by electrostatic adsorption. P(St-AA)/Ag composite microspheres were prepared by the reduction of [Ag(NH3)2]+ ions. The morphologies, types of crystals and valence states of elements of P(St-AA)/Ag composite microspheres were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. The results showed that P(St-AA)/Ag composite microspheres had a good dispersion; Ag on the surfaces of P(St-AA)/Ag composite microspheres displayed a punctate distribution; Ag had a crystal structure of face-centered-cubic and Ag was elemental state.(2) The preparation of PSt/Ag composite microspheres by using sulfonated PSt microspheres as templates. The surfaces of PSt microspheres were modified by using concentrated sulfuric acid as the sulfonating agent. Then PSt/Ag composite microspheres were prepared by redox reactions against the surfaces. The morphologies, types of crystals and valence states of elements of PSt/Ag composite microspheres were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. The results showed that PSt/Ag composite microspheres had good morphologies; Ag on the surfaces of P(St-AA)/Ag composite microspheres displayed a uniform punctate distribution; Ag had a crystal structure of face-centered-cubic and Ag was elemental state.(3) The PSt/PDA/Ag composite microspheres were prepared through the method of modifying PSt microspheres with dopamine. The PSt/PDA microspheres were prepared through the method of modifying the surfaces of PSt microspheres by dopamine. Then the surfaces of PSt/PDA microspheres were coated a layer of Ag by utilizing PSt/PDA microspheres as templates to gain PSt/PDA/Ag composite microspheres by the method of redox. The morphologies, the types of crystals and valence states of elements of the PSt/Ag composite microspheres were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Thermal Gravimetric Analyzer (Tg), High-Revolution Transmission Electron Microscope (HRTEM) respectively. The results showed that PSt/PDA/Ag composite microspheres had a good dispersion, Ag on the surfaces of PSt/PDA/Ag composite microspheres had high dispersion density. And Ag was elemental state and had a crystal structure of face-centered-cubic. The thickness of Ag layer was controlled by changing the concentration of AgNO3 and the amount of PVP.(4) Preparation of PSt/PDA/Ag/PDA composite microspheres. The PSt/PDA/Ag composite microspheres which were obtained by using PSt microspheres that were modified by DA as templates as cores, PDA layers as shells to gain the insulated PSt/PDA/Ag/PDA composite microspheres. The rusults of characterizations showed that PSt/PDA/Ag/PDA composite microspheres had the complete morphologies, there were clearly layers of PDA on the surfaces of PSt/PDA/Ag composite microspheres.(5) Arrangements of particles in an electric field. Experiment was carried out by using PSt/PDA/Ag/PDA composite microspheres as filler particles and using silicone oils as the dispersants. Exploring the impact of filler particles and strength of the electric field on the experiment. The arrangements of particles were observed by the optical microscope in an electric field. The results showed that the arrangement regularity of particles increased when increasing the concentration of particles; when increasing the strength of the electric field, arrangement regularity of particles increased and the time of regular arrangement became more short.(6) The properties of silicone rubbers were modified by PSt/PDA/Ag/PDA composite microspheres. Silicone rubbers containing different amounts of particles were prepared by the method of arranging particles and not arranging particles. The properties of silicone rubbers were characterized by measuring stress-strain curves, dielectric constants and deformations of the silicone rubbers. The results showed that the moduluses of silicone rubbers which were prepared with an electric field were more lower than the moduluses of silicone rubbers which were prepared without an electric field. The dielectric constants and deformations of silicone rubbers which were prepared with an electric field were more better than the dielectric constants and deformations of the silicone rubbers which were prepared without an electric field.