We have recently shown that the addition of single walled carbon nanotubes produces a minimum in the diffusion coefficient with increasing nanoparticle concentration. Initially, tracer diffusion coefficients are suppressed with increasing nanotube content and then increase beyond a critical concentration of ~ 1 vol%. To date, our understanding of why the diffusion coefficient shows this behaviour is limited, although rheological data indicate that whole chain relaxation times are not affected by the presence of the nanotubes. In order to determine whether the diffusion coefficient is changing in response to local monomer dynamics in the presence of nanotubes, we will use QENS to measure the concentration dependence of local dynamics associated with the phenyl side group of the polystyrene chains.