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Preparation of magnetic polymer colloids with Brownian magnetic relaxation |
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| Authors: | Edwin de la Cruz Montoya Maxime J-F Guinel Carlos Rinaldi |
| Institution: | 1. Department of Chemistry, University of Puerto Rico, Mayagüez, PO Box 9000, Mayagüez, PR, 00681, USA 2. Departments of Chemistry and Physics, University of Puerto Rico, PO Box 70377, San Juan, PR, 00936-8377, USA 3. Department of Chemical Engineering, University of Puerto Rico, Mayagüez, PO Box 9000, Mayagüez, PR, 00681, USA 4. J. Crayton Pruitt Family Department of Biomedical Engineering and Department of Chemical Engineering, University of Florida, PO Box 116131, Gainesville, FL, 32611, USA |
| Abstract: | Magnetic polymer colloids (MPCs) consisting of CoFe2O4 nanoparticles (NPs) embedded in a poly(methyl methacrylate) (PMMA) matrix were synthesized by magnetic miniemulsion polymerization. CoFe2O4 NPs were modified with 3-trimethoxysilylpropylmethacrylate and directly emulsified with different concentrations of sodium dodecyl sulfate under ultrasonication for subsequent miniemulsion polymerization. The average diameter of the CoFe2O4/PMMA spheres (about 200 nm) was controlled by varying the amount of surfactant. Thermogravimetric analysis indicated that the magnetic content was in the range of 44 to 73 %. Magnetic properties of the dispersions were investigated by measuring equilibrium magnetization curves and the dynamic magnetic susceptibility as a function of frequency. The MPCs were found to follow the Debye model for the dynamic magnetic susceptibility, with a characteristic time given by the rotational hydrodynamic resistance and thermal energy through the Stokes-Einstein relation. This demonstrates that the MPCs respond to applied magnetic fields by rotating. Due to their uniform size and high magnetic loading, these colloids may be suitable in a variety of applications, including nanoscale mechanical probes and actuators in complex fluids and biological systems. |
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