Synthesis and characterization of well-defined polymer/inorganic nanocomposites

It was shown that the surface of spherical silica nanoparticles could be functionalized with an initiator for ATRP and the macroinitiator particles could be used to initiate the controlled/“living” radical polymerization of several monomers. This was accomplished by first synthesizing near monodisperse silica nanoparticles and modifying the surface of these particles with an initiator suitable for the initiation of ATRP. The polymerization of several different monomers was then conducted from particles of two different diameters. The polymerization of styrene and MMA were conducted using initiator modified 75 nm silica nanoparticles as macroinitiators. It was found that standard ATRP conditions were suitable for the controlled polymerization of styrene, however, the addition of free initiator was necessary to achieve control of the molecular weight and molecular weight distribution when the ATRP of MMA was attempted. The hybrid polymer/inorganic nanoparticles were extensively characterized and it was determined that well-defined polymer chains were grown from the surface of the silica nanoparticles. These polymerizations were repeated using initiator modified 300 nm silica nanoparticles as macroinitiators. Using these larger particles, it was found that the addition of free initiator was required to achieve control for the ATRP of both styrene and MMA. This change in observed polymerization behavior was attributed to a low concentration of initiator in the system due to the very low surface area to mass ratio of the larger particles. The aqueous ATRP of several water soluble monomers was conducted using BIDS-modified 300 nm silica nanoparticles as macroinitiators. The polymer-inorganic nanocomposites were extensively characterized and it was determined that hydrophilic polymer chains were grown from the surface of the silica nanoparticles. The synthetic method presented here is applicable to a range of polymers and inorganic nanoparticles. Many types of inorganic particles can be coated with a silica layer and utilized in this polymerization technique.