Failure mechanism of glassy polymer-nanoparticle composites

A model, well-dispersed nanocomposite of surface-modified cadmium selenide (CdSe) nanoparticles (average core diameter of 3.5 nm) blended into polystyrene is prepared such that entropic forces drive the failure mechanism of the nanocomposite. At an optimal volume fraction (similar to 0.7%) of nanoparticles, the failure strain of the nanocomposite is increased by nearly 60% relative to unfilled polystyrene. The proposed mechanism for this optimal volume fraction is related to the balance of two effects: (1) the decrease in the volume fraction of cross-tie fibrils and (2) the decrease in the extensibility of the craze. These results offer insight into an entropically driven failure of glassy polymer nanocomposites and help guide future design of nanoparticle-based composite materials.