Control of nanoparticle organization in two dimensions by adsorbed polymer layers

Abstract

When a dilute dispersion of relatively monodisperse silica particles is dried on a solid substrate, close-packed arrays are formed. The ordering of the particles results from attractive capillary forces between neighboring particles, and convective transport of particles to the ordered domain during drying. In the presence of adsorbed polymer layers on the particles, the close-packed arrays are disrupted and the particles are disperse upon drying. This is due to steric repulsions of adsorbed polymer layers that prevent close contact of particles during drying, decreasing the probability for formation of the nucleus phase for close-packed ordering. Using electron spectroscopy imaging in a transmission electron microscope, we directly observed the adsorbed polymer layers on the dry dispersion. The thickness of the adsorbed layer and its effect on particle dispersion are investigated as a function of polymer concentration, chain length and solvent quality.

Acknowledgements: The authors thank FAPESP, Pronex/Finep/MCT and CNPq for financial support. This is a contribution from the Millennium Institute for Complex Materials.