Thin polymer-layer decorated, structure adjustable crystals of nanoparticles.

Flattened polymer chain decorated crystals of nanoparticles (NPs) are observed for polymer-NP mixtures confined between two parallel substrates. In order to minimize the entropy loss, polymer chains instead of NPs aggregate at the substrate surfaces when the number of NPs is high enough to have the conformation of chains significantly disturbed. Increasing NP concentration to be much higher than that of polymer chains leads to an ordered arrangement of NPs in the central region, which are sandwiched between two thin layers of polymer chains. A scaling model regarding polymer chains consisting of packed correlation blobs is provided to clarify the physics mechanism behind the formation of thin polymer layer and the crystallization of NPs. The order structure of the crystallized NPs is shown to be switchable through an adjustment of the bulk concentrations of polymer chains and NPs.