| Electrorheological fluids (ERF) are a kind of smart materials which are composed of high-dielectric-constant and low-conductivity solid particles dispersed in insulating liquid. Under a fixed shear rate, appearance viscosity increases rapidly with the increase of electrical field and this response is both reversible and controlled easily. So this phenomenon is called electrorheological effect. ERF can be applied in many areas, such as switch, clutch, brakes, valve and other intelligence-control areas. In this thesis, strontium titanate (SrTiO3)/polymethyl methacrylate (PMMA) composite particles were firstly prepared. Then the properties of ERF which was doped by organical montmorillonite (O-MMT) were studied. In addition, the apparatus for testing viscosity and observing polarization phenomenon were reformed. Several subjects were studied in details in this thesis. Firstly, strontium titanate (SrTiO3)/Polymethyl methacrylate (PMMA) composite particles were prepared in emulsion polymerization by using NDZ-311 as a coupling agent and sodium dodecyl sulfate (SDS) as a surfactant and emulsifying agent, then were characterized by FT-IR and SEM et al. Secondly, the theories on PMMA coating SrTiO3 were studied and the structural model about SrTiO3/PMMA composite particles was expounded. Thirdly, SrTiO3/PMMA ER fluid was prepared and the ER properties were researched. Additionally, the influences including the size and content of SrTiO3/PMMA particles, the content of NDZ-311 and SDS, and base liquids on ER properties were discussed. Fourthly, ER properties of O-MMT and MMT doping ERF were compared. Dielectric properties and ER effect were especially discussed. Besides them, ER theory was tried to explain. It was shown that PMMA had already coated SrTiO3, and 5% O-MMT doping could improve ER effect largely and its increment was 14 times than that of ERF not doping. Meaning-time, it was founded that cooperatation effect exists in O-MMT, SrTiO3/PMMA composite particles and castor oil.
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