(556d) Atomic Transfer Radical Polymerization Synthesis of Magnetorheological Fluids

Novel magnetorheological (MR) fluids are synthesized using surface initiated atom transfer radical polymerization (ATRP) of poly (butyl acrylate) on iron particles. The surface polymerization involves two steps, immobilization of initiator 2-4(-chlorosulfonylphenyl)-ethytrichlorosilane (CTCS) on the surface of iron particles and graft polymerization of butyl acrylate from the surface. The surface polymerization is characterized by Fourier transform IR and scanning electron microscopy. This novel MR fluid has controllable off-state viscosity and high shear yield stress. Surface polymerization on iron particles using ATRP can significantly reduce iron particle settling and improve the stability of MR fluids. The polymerization kinetics of bulk butyl acrylate are studied using differential scanning calorimetry. It is found that the molecular weight and conversion can be controlled by the molar ratio of monomer to initiator, reaction temperature and time. The reaction is first order determined by the plot of against polymerization time. The overall activation energy is found to be 126kJ/mol by Kissinger's Method.