Nanoparticle Reshaping in Polymer Nanocomposites: Quantifying the Effect of Polymer Mechanics on Gold Nanorod Surface Diffusion Dynamics

Thermal reshaping via surface diffusion is an important phenomenon in gold nanorod polymer composites. Observed reshaping dynamics at a given temperature depend strongly on the nanorod environment, as evidenced by observed exponential time constants in different systems ranging from seconds to days. We have measured the shape dependent extinction spectra in nanocomposites having different gold nanorod morphologies and different matrix mechanical properties. We show that a surface diffusion model is sufficient to explain the intial rate of shape transformation in all cases, but that the ultimate amount of reshaping depends on the matrix and the initial morphology of the nanorods. The interaction of grafted ligands with the surrounding matrix plays an important role in the thermal reshaping dynamics as well as the interpretation of the scattering spectra in these systems.