Glass transition of polymer-nanocrystal thin film mixtures: role of entropically directed forces on nanocrystal distribution.

The connection between the average properties of a polymer/nanocrystal hybrid material and the nanocrystal spatial distribution is shown. Specifically, a property such as the glass transition temperature, Tg, is shown to vary by as much as 65 degrees C through only changes in the spatial distribution of the nanocrystals. Considerable control can be exercised over the nanoparticle spatial distribution. In addition, we show that while the Tg of a thin film hybrid material may be enhanced in relation to the pure bulk system, the bulk nanocomposite analog shows a reduction in Tg. These findings have broad implications with regard to the design of materials with required properties.