Tailoring the properties of grafted silver nanoprism composites

We present simple phenomenological evidence linking the optical and tensile properties of nanocomposites of metallic particles in polymer melts to their method of preparation. We made films containing silver nanoprisms embedded in a matrix of poly (vinylpyrrolidone), PVP, or poly (ethylene oxide), PEO, by solvent casting or spin coating. Microscopy imaging revealed that the silver nanoparticles can either disperse uniformly or self-assemble into different structures within the polymer matrix. The type of arrangement depends on the particles concentration, phase of the matrix (amorphous or crystalline) and matrix-particle interactions. In PVP edge-to-face arrangements were observed whereas in PEO the nanoparticles preferentially segregated at the crystal boundaries. Spin coating was found to induce a certain degree of local alignment of the nanoparticles, however the mechanical properties as measured by tensile strain, were not affected at all. The different Ag particle arrangement led to large changes in the optical properties of the composites, as characterized by vis-NIR absorbance spectroscopy. The large sensitivity of the optical properties and virtual insensitivity of mechanical properties constitute design criteria for potential applications