The development of composite materials with nanoparticles has been studied in recent years. But studies on the dispersion of magnetic nanoparticles in a polymer matrix are still difficult to achieve today. Our goal is to design this kind of material with good dispersion and high loading rates. We are particularly interested in nanoparticles dispersed in a matrix of PMMA with a mass loading rate of 1%. Poly(methylmethacrylate) is synthesised from the surface of magnetic nanoparticles by Reversible Addition-Fragmentation Chain Transfer (RAFT) using a silanic coupling agent with trithiocarbonate RAFT agent. First, magnetic nanoparticules were activate by nitric acid to create hydroxyl groups at their surface. Then, the RAFT agent is anchored to magnetic nanoparticles via condensation reactions. Thermogravimetric analysis and diffused reflection FT-IR were used to confirm and measure the grafting reaction. These results show the importance of the activation by nitric acid and a better grafting yield with collecting by solvent evaporation. The RAFT polymerisation of methyl methacrylate was carried out in the presence of AIBN in THF. The grafting density was determinated by thermogravimetric analysis, mechanic properties were measured by traction tests and molar mass and polydispersity index were caracterised by GPC analysis. First results show that composite material compared to matrix of PMMA is more elastic due to nanoparticules. PMMA has a deformation of 2% and up to 4% with nanoparticules. The next step is to improve mass loading rate to 5% and 10% and then to determinate magnetic properties of these materials.