Synthesis assembly and thermo responsivity of polymer functionalized magnetic cobalt nanoparticles This thesis mainly covers the synthesis surface modification magnetic field induced assembly and thermo responsive functionalization of superparamagnetic Co NPs initially stabilized by hydrophobic small molecules oleic acid (OA) and trioctylphosphine oxide (TOPO) as well as the synthesis of both superparamagnetic and ferromagnetic Co NPs by using end functionalized polystyrene as stabilizer. Co NPs due to their excellent magnetic and catalytic properties have great potential application in various fields such as ferrofluids catalysis and magnetic resonance imaging (MRI). Superparamagnetic Co NPs are especially interesting since they exhibit zero coercivity. They get magnetized in an external magnetic field and reach their saturation magnetization rapidly but no magnetic moment remains after removal of the applied magnetic field. [...]