The preparation of silica-poly(norbornene) nanocomposites by surface initiated polymerization

摘要

One significant challenge for the application of nanoparticle technologies is controlling interparticle aggregation of particles with diameters under 100 nm. The two primary means to control aggregation are steric effects and charge stabilization. Steric effects require the presence of long nonpolar chains with no attractive interactions that influence interpartical correlations through their excluded volume. Charge stabilization uses the repulsive electrostatic forces of a charged surface. The prototypical nanoparticle with these characteristics is colloidal silica. In order to access both types of stabilization on must overcome the inherent difficulties of changing the hydrophobic/hydrophilic balance of the surface while changing the solvent environment. Our approach is to use a multi-step reaction where particle properties are changed gradually. This paper will report one such synthesis where the surface of silica nanoparticles is modified using 5-(bicycloheptenyl)-triethoxysilane to form a macroinitiator for the polymerization of poly(norbornene). These nanocomposites have greatly improved stability against particle aggregation.