Synthesis and electrorheological characterization of emulsion polymerized SAN-clay nanocomposite suspensions

Styrene-acrylonitrile (SAN) copolymer-clay nanocomposite was synthesized by emulsion polymerization, which is the easiest method of intercalation (e.g ., melt or solution intercalation). Existence of the intercalated polymer w as verified by Fourier transform-infrared spectroscopy and X-ray diffractio n (XRD) analysis. From XRD, we confirmed the insertion of styrene-acrylonit rile copolymer between the interlayers of clay, whose separation consequent ly becomes larger than that of the polymer-free clay. Thermogravimetric ana lysis showed that the thermal stability of the organic polymers was sustain ed. Using electrorheological (ER) fluids composed of intercalated particles and silicone oil, we observed typical ER behavior, such as higher shear st ress in the presence of an electric field and increasing yield stress with particle concentration. We further observed the critical shear rate at whic h the ER fluids exhibit pseudo-Newtonian behavior.