Ordering of binary polymeric nanoparticles on hydrophobic surfaces assembled from low volume fraction dispersions

Well-ordered two-component nanoparticle (NP) patterns are generated on hydrophobic surfaces from mixed particle suspensions of very low volume fraction by simple drop-casting and self-assembly during solvent evaporation. A range of NP sizes (520-60 nm), volume fractions, and particle chemistries (aminated, carboxylated, sulfated) are tested, and in all cases, hexagonally packed patterns of the larger NP interdispersed with the smaller NP are obtained. The mechanism for formation appears to be entropically driven since the pattern formation occurs over a wide pH range (4-10) and is thus independent of particle surface charge. The nanopatterns show promise as model systems for studying interfacial phenomena such as protein adsorption and cell adhesion.