Recently, organic/inorganic composites have been important candidates for electrorheological (ER) fluids due to various unique heterogeneous physical properties. Therefore, in this work, nano-sized PMMA spheres coated by disk-liked laponite were synthesized by surfactant free emulsion polymerization. This hydrophilic laponite clay which possesses a lateral diameter of 25nm and 1nm in thickness was used as a stabilizer while polymerizing PMMA in distilled-water. By employing water-soluble potassium persulfate as an initiator, the size of synthesized PMMA nanospheres was in the range of 500nm to 800nm. SEM and TEM images were applied to investigate whether the surface of PMMA was covered by the laponite used as stabilizer. TGA data was used to confirm both thermal stability of the composite and weight percent of laponite appeared in the PMMA surface. Finally, the prepared nano-sized PMMA spheres were adopted as ER fluid by dispersing them in insulating silicone oil. ER performance was analyzed by using an optical microscope (OM), in which chain-like structure was observed due to the conductive clay surface of particle when an external electric field was applied.

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