(722ag) Surface Polymerization of Iron Particles for Magnetorheological Elastomers (MREs) and Their Potential Application as Sensors

Magnetorheological Elastomers (MRE) are intelligent materials which are synthesized from a polymer matrix and magnetic particles. MRE have viscoelastic, magnetorestrictive, and magnetoresistive properties which can be used for vibration isolator and sensing devices. This is possible because of the alignment of the magnetic particles in the polymer matrix by induction of magnetic field. In addition, changes in the magnetostrictive and magnetoresistive properties are controlled by varying the magnetic field. Chain-like magnetic particles provide rapid time response of milliseconds. The magnetostrictive effects, include stiffness and dimension change, of MRE is caused by changing the distance between magnetic particles in the elastomer matrix under the influence of an external magnetic field. This phenomenon is suitable for the vibration isolator application. Another phenomenon, the magnetoresistive effect, is important for sensor applications. The magnetoresistive effect is due to the change in electric impedance of the material that caused by magnetic field. The impedance consists of a real that represents resistance and imaginary part that represents the capacitance. The addition of an external force onto magnetized MRE will cause the deformation of the chain-like structure of magnetic particles. The electric properties of MRE will be changed by deformation of the chain-like structure. The magnetic particles have been coated using fluorinated polymer by atom transfer radical polymerization (ATRP) technique in order to prevent the oxidation and durability of MREs. The materials have been characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). As a result, the impedance value decreases by increasing magnetic field, iron concentration, and applied force. In addition, the ATRP technique provided better interaction between elastomer and surface coated iron particles in compared with ordinary radical polymerization.