Micellar assemblies from amphiphilic polyurethanes for size-controlled synthesis of silver nanoparticles dispersible both in polar and nonpolar media

A size-controlled synthesis of silver nanoparticles (AgNPs) dispersible in polar and nonpolar media was carried out in micellar assemblies from amphiphilic invertible polyurethanes (AIPUs) based on poly(ethylene glycol) as a hydrophilic constituent and polytetrahydrofuran as a hydrophobic constituent. At a low concentration, AIPUs form micelles with a hydrophilic interior and a hydrophobic exterior. As concentration increases, individual micelles self-assemble into micellar assemblies with hydrophilic interior and hydrophobic exterior domains. It was shown that these domains can be applied simultaneously as nanoreactors and colloidal stabilizers to synthesize size-controlled batches of AgNPs in a nonpolar solvent. Size control and narrow particle size distribution can be facilitated by changes in the AIPU composition, macromolecular configuration, and polymer solution concentration. Depending on the length of polymer hydrophilic and hydrophobic fragments, and fragment distribution along the macromolecule, the size of fabricated AgNPs has been changed from 6 to 14 nm. Owing to the invertible properties of polyurethanes, the synthesized silver nanoparticles can be successfully dispersed in either polar or nonpolar media, where they form stable colloidal solutions.