Effect of Polymer Ligand Molecular Weight on Polymer-Coated Nanoparticle Location in Block Copolymers

Abstract

Gold nanoparticles (Au−PS) coated with an areal chain density Σ of end-attached polystyrene (PS) chains of different molecular weights (Mn) are added to a lamellar diblock copolymer of poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) to determine the critical areal chain density ΣC below which the Au−PS nanoparticles adsorb to the PS-b-P2VP interface. Gold nanoparticles coated by thiol end functional polystyrene homopolymers (PS−SH) with Mn ranging from 1.5 to 13 kg/mol are synthesized with various areal densities of PS−SH chains on the nanoparticle surface. The particles are incorporated into a PS-b-P2VP diblock copolymer with Mn = 196 kg/mol. The P2VP block has a more favorable interaction with a bare gold particle surface than does the PS block, and this interaction becomes important as the coverage of gold particles by PS−SH decreases, leading to adsorption of the Au−PS to the interface below a critical areal chain density ΣC. ΣC decreases from 3.1 to 0.9 chains/nm2 as the Mn of PS−SH chains increases from...