Covalent Nanoparticle Assembly onto Random Copolymer Films

Abstract

We present a novel class of nanoparticle-decorated surfaces: amine-functionalized silica nanoparticles covalently attached to poly(styrene-random-acrylic acid) films and carboxylic acid-terminated self-assembled monolayers (SAMs). The dependence of the particle attachment kinetics on the concentration of particles in solution and acrylic acid moieties in the polymer backbone was investigated and was compared to the observed kinetics with SAM substrates. The kinetics on the polymer films included three distinct stages, which were governed by the acrylic acid concentration-dependent morphological changes of the films under the reaction conditions. The first stage was an induction period with little change in the particle coverage with time, followed by a rapid rise in the coverage, and finally a plateau. The maximum coverage achieved for the polymer films, 70%, was nearly twice that of the SAM substrates, which followed diffusion-limited coverage kinetics prior to reaching saturation. This enhanced coverage is attributed to the swelling of the acrylic acid groups at the film surface in the reaction solvent, which increases the surface area and roughness of the substrate. This approach is a reproducible way of preparing nanoparticle-decorated, chemically robust surfaces with controlled coverages and have potential applications for controlling surface wettability, optical properties, and cellular adhesion.