A general synthetic approach for obtaining cationic and anionic inorganic nanoparticles via encapsulation in amphiphilic copolymers

A series of amphiphilic copolymers with variable charge densities on their backbone is synthesized. Positively charged N,N,N-trimethylammonium-2-ethyl methacrylate iodide or negatively charged 2-(methacryloyloxy)ethylphosphonic acid and lauryl methacrylate are used as building blocks. When wrapped around hydrophobically capped inorganic nanoparticles (NPs), the latter are able to disperse in aqueous solutions. Using this method, positively as well as negatively charged colloidal NPs can be synthesized in a reliable way. The method presented herein allows the charge on the NPs to be adjusted to different negative and positive values by using polymers with a variable ratio of charged monomers and lauryl methacrylate. Virtually all kinds of hydrophobic inorganic NPs could be coated with these amphiphilic polymers. The coating procedure is demonstrated for Au particles as well as for CdSe/ZnS quantum dots. To date, wrapping amphiphilic polymers around NPs has led only to anionic NPs. The polymers synthesized in this work allow for positively charged NPs with a high colloidal stability.