Silanization as a versatile functionalization method for the synthesis of polymer/magnetite hybrid nanoparticles with controlled structure

Abstract

We compare the use of different trimethoxysilane compounds for the surface functionalization of magnetite nanoparticles and their subsequent incorporation in hybrid particles formed by in situ polymerization. For the encapsulation of inorganic nanoparticles via miniemulsion polymerization, surface functionalization of the inorganic material is necessary to hydrophobize the otherwise hydrophilic inorganic material and to compatibilize it with the polymer. Hydrophobic magnetite nanoparticles are usually prepared by surface functionalization with oleic acid, which leads to effective hydrophobization, but offers only limited control over the structure of the hybrid particles. As an alternative, we report the encapsulation of magnetite particles functionalized with 3-methacryloxypropyl trimethoxysilane (MPS) or octadecyl trimethoxysilane (ODTMS). The influence of the surface functionalization on the compatibility of the inorganic particles with different polymers is investigated by determining the solid content of the dispersions and the magnetite content of the hybrids. The morphology of the hybrid materials is studied by transmission and scanning electron microscopy. MPS-functionalized magnetite particles are distributed homogeneously within the polymers, while ODTMS and oleic acid lead to the formation of Janus particles. These observations are similar regardless of the polymer, which demonstrates that the functionalization is the decisive factor in tuning the structure of hybrid nanoparticles.