Surface Grafting of Polymers onto Nanoparticles in a Solvent-Free Dry-System and Applications of Polymer-grafted Nanoparticles as Novel Functional Hybrid Materials

Abstract

For the prevention of environmental pollution and simplification of reactions, scale-up synthesis of polymer-grafted inorganic nanoparticles in a solvent-free dry-system is reviewed. The grafting of polymers onto nanoparticles in a solvent-free dry-system was achieved by spraying monomers onto nanoparticles having initiating group. After the reaction, unreacted monomer and by-products were removed under high vacuum. For example, grafting of hyperbranched poly(amidoamine) (PAMAM) was successfully achieved using dendrimer synthesis methodology in a solvent-free dry-system. The percentage of PAMAM grafting onto the nanoparticle surface was 141% with repeated reaction cycles of 8-times. In addition, radical graft polymerization of vinyl monomers onto silica nanoparticles was achieved by spraying the monomers onto silica nanoparticles containing azo and peroxycarbonate groups in a solvent-free dry-system. The formation of ungrafted polymer was depressed in comparison with graft polymerization in solution: the grafting efficiency was 90–95%. PAMAM-grafted silica dispersed uniformly in epoxy resin and has an ability to cure the epoxy resin. Glass transition temperature of cured material was much higher than that of the material cured by conventional curing agents. The immobilization of norbornadiene, capsaicin, and flame retardant onto PAMAM-grafted nanoparticle and the properties of the resulting materials are also described.