Preparation of silver nanoparticles templated from amphiphilic block copolymer-based hexagonal liquid crystals

Preparation of silver nanoparticles templated from amphiphilic tri-block copolymer poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide)-based hexagonal liquid crystals is reported. Oxyethylene groups of PEO blocks play an important role in the reduction of metal ions, whereas the long-ranged ordered structure of liquid crystal lead to formation of organized nanostructures. The phase behaviors of hexagonal phase and the morphology of silver nanoparticles are studied, respectively, by small-angle X-ray scattering (SAXS), polarized optical microscope (POM) and transmission electron microscope (TEM). Addition of anionic surfactant, sodium di-2-ethylhexylsulfosuccinate (AOT), into the copolymer systems does not destroy the hexagonal phase but reduce the lattice spacings. This effect, combined with the interaction between negative headgroups of AOT and Ag+ ions, prevents silver nanoparticles from aggregation to large ones. Effects of surfactant concentration and reaction time on the formation of silver nanoparticles are also discussed.