Controllable Synthesis of a Well-defined Polypropylene Grafted Silica Nanoparticles and Its Effect on Crystallization Behavior of Polypropylene

Well-defined polypropylene grafted silica nanoparticles (PP- g -SiO 2 ) were prepared through the reaction of maleic anhydride grafted polypropylene (PP- g -MAH) with amino-functionalized silica (SiO 2 -NH 2 ) by the ‘grafting-to’ method. The grafting density of PP- g -SiO 2 is found to be controlled by the concentration of silane coupling agent 3-[2-(2-aminoethylamino) ethyl amino] propyl trimethoxy silane (TAMS). The maximum grafting density of grafted PP- g -MAH chains with molecular weight of 9100 g/mol could reach 0.34 chains/nm 2 , when the critical concentration of TAMS was 0.0194 mol/L. The critical concentration of TAMS can be explained by the maximum amounts of primary amino groups, which can totally react with PP- g -MAH on the surface of SiO 2 -NH 2 , when the silane monolayer is formed. The synthesized PP- g -SiO 2 with different molecular weights was mixed with PP by solution mixing to form a series of nanocomposites. The crystallization temperature ( T c ) of nanocomposites increased significantly with the particle loading. The PP- g -SiO 2 with high molecular weight of grafted chains exhibits a high nucleation ability at 1 wt% nanoparticle loading in PP/PP- g -SiO 2 nanocomposites. In summary, we provide an effective method to synthesize the well-defined PP- g -SiO 2 with controlled grafting density, which shows excellent nucleation ability.