Effect of areal chain density on the location of polymer-modified gold nanoparticles in a block copolymer template

A strategy for controlling the location of gold nanoparticles within block copolymer domains through varying the surface coverage of gold nanoparticles by end-attached polymer ligands is described. Gold nanoparticles coated by short thiol end functional polystyrene homopolymers (PS-SH) (M-n = 3.4 kg/mol) are incorporated into a poly(styrene-b-2-vinylpyridine) diblock copolymer template (PS-b-P2VP) (M-n = 196 kg/mol), the P2VP block of which has a more favorable interaction with a bare gold particle surface than does the PS block. The areal chain density of the PS-SH ligands on gold particles is varied by changing the mole ratio of PS-SH chains to gold atoms. It is found that the areal density of PS chains on the gold particles is critical to controlling their location in block copolymer templates. PS-coated gold nanoparticles with PS chain areal density higher than 1.6 chains/nm(2) are dispersed in PS domains of PS-b-P2VP while they are segregated along the interface between PS and P2VP domains of PS-b-P2VP for PS chain areal density < 1.3 chains/nm(2). Even at extremely low grafting densities of polymer ligands, gold nanoparticles can be stabilized in solution, and self- assembly of these nanoparticles can be controlled within the block copolymer template.