Effect of solvent exchange on the stability of sterically functionalized magnetite nanoparticles in poly(methyl methacrylate)-solutions and resulting spray dried composites

In this study highly filled nanoparticle-polymer-composites consisting of the polymer poly(methyl methacrylate) and magnetite nanoparticles are synthesized via the solution and spray drying method. The synthesis process is carried out for two different solvents, dichloromethane and ethyl acetate, and the resulting suspensions and composites are compared to each other. The preparation of the composites consists of the following steps: First the magnetite nanoparticles are precipitated in an aqueous phase. In the next step the nanoparticles are coated with ricinoleic acid for stabilization and are transferred to the organic solvent dichloromethane. In a rotating evaporator the solvent dichloromethane is exchanged with ethyl acetate. Finally, the nanoparticles in the respective solvent and dissolved polymer are mixed and spray dried.
The stability of the nanoparticle suspensions is characterized using thermogravimetric and photometric analyses. The specific surface of spray dried composites is determined via BET measurements and the distribution of the nanoparticles is assessed with BSE-SEM imaging and laser diffraction.
The stability of the nanoparticles is independent of the examined solvents. Both solvents provide a homogeneous distribution of nanoparticles in the composite at high filler concentrations.