Optical Properties of Ag/Polyvinylidene Fluoride Nanocomposites: A Theoretical Study

Abstract

Metal/polymer nanocomposite materials are interesting because of their ability to combine the versatility of a polymer matrix with the field-response properties of metallic nanoparticles. New materials with distinct and sometimes highly tunable properties are thus obtained. Here we employed density functional theory-based optical response calculations to study their optical response properties. We used a simple model comprised of small silver nanoparticles enshrouded in polyvinylidene fluoride and calculated the imaginary part of the dielectric constant and related optical constants from dipolar interband transitions. The effects of varying inclusion volume ratios and nanoparticle shapes and sizes are discussed. We found that most of the material response in the optical regime was due to the presence of the metallic inclusion, which introduced both occupied and virtual orbits into the large polymer band gap. Thus, higher inclusion volume fractions generally led to stronger composite optical response. Changes in spectra of monodisperse systems, with the size and shape of the inclusions, correlated well with nanoparticle quantum confinement models. A simple model of a more polydisperse nanocomposite showed that optical properties correlated best with interparticle distances along the field direction and with nanoparticle orientation with respect to this direction