Surface-initiated SET living radical polymerisation for the synthesis of silica–polymer core–shell nanoparticles

Abstract

We report the use of surface-initiated single-electron transfer living radical polymerisation (SI SET-LRP) to prepare inorganic–organic core–shell nanoparticles with functional grafted chains of high molecular weight. The potential of SI SET-LRP is demonstrated by the preparation of a series of silica–polymer core–shell materials from a silica nanoparticle template bearing a bromo ester initiating group in the presence of a free initiator, with detailed kinetic investigations using methyl acrylate and tert-butyl acrylate. Under optimised polymerisation conditions, concentrated polymer brushes with grafting densities as high as 0.8 chains per nm² and relatively high molecular weight polymer grafts (degree of polymerisation, DP_n, up to 1000) were achieved whilst employing a heterogeneous copper(0) wire catalyst at low polymerisation temperatures. Under optimal conditions, the polymer shell grows similarly to the free polymer with increasing monomer conversion to produce well-defined monodisperse particles with a narrow size distribution. The particle uniformity results in the formation of particle assemblies that display long-range 2D and 3D order, as characterised by electron microscopy.