Grafting of hyperbranched aromatic polyamide onto silica nanoparticles

Hyperbranched aromatic polyamide grafted nano-silica particles were successfully prepared via “one-pot” melt polycondensation. The particles were firstly treated with a silane coupling agent to introduce amine groups as the growth points, and then grafting of the hyperbranched polymers started from the modified surface. The percentage grafting can be as high as 32.8%. The key reaction conditions, including feeding ratio, reaction temperature and time, were carefully investigated to determine a set of optimal grafting parameters. It was found that the significant steric hindrance between the hyperbranched polymers during graft polymerization played a key role in controlling molecular structure of the grafted polymers, while adsorption of grafting monomer onto SiO₂ particles prior to the reaction facilitated higher degree of branching and apparent molecular weight of ungrafted polymers.