Optically anisotropic polyethylene-gold nanocomposites.

Gold colloids coated with a self-assembled monolayer of an alkanethiol were introduced into a polyethylene matrix by means of solution-casting techniques. We oriented the resulting nanocomposites by uniaxial drawing in the solid state. The absorption spectra of the drawn nanocomposites in the visible wavelength region were found to depend strongly on the polarization direction of incident light. The materials appeared, for instance, red or blue if the light was polarized perpendicular or parallel, respectively, to the drawing axis. The observed optical anisotropy is thought to originate in the morphology of the composites that composed uniaxially oriented, pearl-necklace arrays of nanoparticles with a high aspect ratio, as observed in transmission electron microscopy. It is shown that the polymer-inorganic nanocomposites can be employed as color polarizing filters.