Magnetic macro-initiators

Abstract

Macro-initiators were prepared using three magnetic nanoparticles, Fe₃O₄, FeCo, or Co. Azo free radical initiators were grafted onto the magnetic particles in a two-step reaction utilizing alkoxysilane and ambient temperature esterification reactions. The magnetic initiators (MI) were characterized using IR, DSC, TGA, SEM with EDAX, and DLS. An alternating gradient magnetometer gave saturation magnetization (M_s) values of 42.1, 178.3, and 36.1 A m² kg⁻¹ for Fe₃O₄, FeCo, and Co MIs respectively. Bulk polymerization of styrene was used to assess the effectiveness of MIs in free radical polymerization. Molecular dynamic (MD) simulations were performed on the magnetic macro initiators to determine the feasibility of initiating free radical polymerization by application of an external AC MF. The MD simulations showed that magnetically induced polymerization is possible with a minimum force of 62 kcal mol⁻¹ Å⁻¹ required to be applied to the core of the MI in order to decompose the C–N bond of the azo group, producing free radicals.