Polymer ligand exchange to control stabilization and compatibilization of nanocrystals.

Abstract

We demonstrate polymer ligand exchange to be an efficient method to control steric stabilization and compatibilization of nanocrystals. A rational design of polymer binding groups and ligand exchange conditions allows to attach polymer brushes with grafting densities >1 nm(-2) to inorganic nanocrystals for nearly any nanocrystal/polymer combination using only a few types of binding groups. We demonstrate the potential of the method as an alternative to established grafting-from and grafting-to routes in considerably increasing the stabilization of inorganic nanocrystals in solution, to prepare completely miscible polymer nanocomposites with a controllable distance between nanoparticles, and to induce and control aggregation into percolation networks in polymeric matrices for a variety of different nanocrystal/polymer combinations. A dense attachment of very short polymer ligands is possible enabling to prepare ordered nanoparticle monolayers with a distance or pitch of only 7.2 nm, corresponding to a potential magnetic storage density of 12.4 Tb/in(2). Not only end-functionalized homopolymers, but also commercially available copolymers with functional comonomers can be used for stable ligand exchange, demonstrating the versatility and broad potential of the method.