The goal of this project was to study the optical properties of polymer nanocomposites using discrete dipole approximation (DDA) calculations. This project examines polymer composites containing polymer-grafted spherical gold nanoparticles inside of a polymer matrix. Each nanoparticle has PMMA chains attached to its surface, which changes how the nanoparticles interact with the SAN matrix and allows for controllable composite morphologies. These different morphologies result in different optical properties of the material, which can be captured through the DDA calculations.

The DDSCAT software was used to model the nanoparticles as a core-shell structure. The DDA calculations were performed with multiple PMMA graft molecular weights, in order to observe the effects of increasing polymer graft length on the nanoparticles’ optical properties. The simulations showed that as the length of the PMMA grafts increases, the peak light extinction efficiency of the nanoparticle decreases. The wavelength corresponding to the peak also decreases slightly. This showed that the optical properties of polymer-grafted nanoparticles can be accurately modeled with DDSCAT simulations.