Preparation Of PS/PMANI Core-shell Microspheres And Their Electrorheological Performances

Electrorheological(ER)fluids are a kind of smart fluids whose rheological properties,such as shear stress,shear viscosity and moduli,can be varied by an applied electric field.Owing to sensitive and reversible transition in rheological properties,ER fluids show a great application prospect in engineering areas.In this paper,several groups of polystyrene/poly(2-methylaniline)core-shell microspheres were prepared by controlling the reaction conditions and their electrorheological properties were studied.Firstly,PMANI particles were prepared by a typical procedure and ER properties were tested.And then,PS/PMANI core-shell microspheres were synthesized by a seed emulsion polymerization.Different amount of monomer,2-methylaniline,and different kinds of initiators,mmonium persulfate and iron nitrate nonahydrate,were used to prepared several groups of core-shell microspheres with different thickness of shell layer and different surface morphologies.Morphologies,chemical structures and thermal properties of core-shell microspheres were detected by SEM,FT-IR and TG respectively.SEM images showed that the morphology of PMANI was irregular,however the PS/PMANI was regular and monodisperse.With the increment of the amount of2-methylaniline,the thickness of PMANI layer became thicker.By using different kind of initiators,ammonium persulfate and iron nitrate,smooth and sea urchin-like PS/PMANI particles can be prepared.PMANI showed typical ER behavior.To describe the ER behavior of PMANI ER fluid,Bingham model and Cho-Choi-Jhon model were used and the CCJ model can describe the ER behavior in more detail.ER fluids based on PS/PMANI core-shell microspheres with different content of PMANI performed remarkable ER performance and with the increment of the content of PMANI,ER fluid can showed higher yield stress.On the other hand,the ER fluid with sea-urchin like microspheres exhibited a much higher yield stress than that showed by the smooth particles,however a higher off-field viscosity can be observed at the same time.