Why Structure Matters - Controlling the Properties of Nanoparticle Hybrid Materials

The complementary physical properties of the distinct constituents render polymergrafted nanocrystals (PGNPs) intriguing materials systems in which property characteristics can be tuned over a wide range from hard particulate to soft polymer-type. Here we demonstrate that dependent on the molecular weight and the graft density of the grafted polymer chains, three characteristic regimes of PGNPs are observed: (1) hard-sphere type colloidal crystalline with the formation of cracks driven by short-range interactions, (2) plastic mesocrystalline with the crazing behaviors by chain entanglement, or (3) disordered structure with soft-polymer type interactions. In addition to controlling the mechanical properties of PGNPs, grafted chains can have a key role in mediating their gradual transformation into more ordered microstructures from nanoparticles with energetically unfavorable property (i. e., activation barrier for crystallization induced by polydisperse nanoparticles [1, 2]).