Self-Assembly of Maltoheptaose-block-Polystyrene into Micellear Nanoparticles and Encapsulation of Gold Nanoparticles

The present paper discusses the controlled self-assembly of sugar-containing block copolymer, maltoheptaose-block-polystyrene (MH1.2k-b-PS4.5k), into micellar nanoparticles of ca. 30 nm radius in aqueous media and their possibility of gold encapsulation. Micellar association of MH1.2k-b-PS4.5k into nanoparticles was demonstrated by mixing a large amount of water (MH-selective solvent) with a solution of MH1.2k-b-PS4.5k in a mixture of tetrahydrofuran (THF) (PS-selective solvent) and water with a certain weight fraction [4:1 (w/w) THF/water], where MH1.2k-b-PS4.5k exists as well-swollen single chains, followed by evaporation of THF. The mean hydrodynamic radii (R-h) of the nanoparticles were determined by dynamic light scattering (DLS) to be ca. 30 and 80 nm depending upon the method of preparation. The resulting nanoparticles were clearly visualized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and field emission gun-scanning electron microscopy (FEG-SEM) imaging and complemented by nanoparticle tracking analysis (NTA) using a Nano Sight instrument. The preliminary study of the self-assembly of MH1.2k-b-PS4.5k in the presence of gold nanoparticles functionalized with PS chains grafted on their surface indicated potential possibilities of encapsulation of gold nanoparticles into the block copolymer nanoparticles in aqueous media.