ИСТИНА

A fast route to transfer Au nanoparticles from aqueous to organic media is proposed based on the use of a high molecular mass diblock copolymer of styrene and 2- or 4-vinyl pyridine for ligand exchange at the nanoparticle surface. The method enables the preparation of stable sols of Au nanorods or nanospheres with sizes of up to tens of nanometers in various organic solvents (CH2Cl2, CHCl3, benzene, toluene, THF). The stability of Au nanoparticles is proven by multiple cycles of vacuum drying and redispersing. By comparing the optical absorbance spectra of Au hydro- and organosols with the data of numerical simulations of the surface plasmon resonance, we find that nanoparticles do not aggregate and confirm the transmission electron microscopy data regarding their shape and size. The proposed approach is used for preparing hybrid composites, in which the microphase-separated block copolymer simultaneously plays the role of a stabilizer that prevents the aggregation of nanoparticles and of a matrix providing their selective arrangement in the domains of a given type. Small (~ 5 nm) organodisperse nanospheres can also be introduced into the composite by replacing a labile stabilizer used in the synthesis process with the diblock copolymer. Thin films of Au nanospheres or nanorods in block copolymer matrices are made by spin casting followed by solvent vapor annealing. The content of Au nanoparticles in the composites is up to 5% by mass, they are dispersed and located mainly within the vertical or horizontal cylindrical domains of vinylpyridine, while the nanospheres are localized near the domain walls and the nanorods are generally oriented perpendicularly to the cylinder axis. These data are discussed regarding the results of the recent simulations by dissipative particle dynamics. Thus, stable polymer-based composites with large Au nanoparticles can be prepared without the use of strong thiol and amine surfactants.