Holographic grating relaxation studies of probe diffusion in a polymer blend

Probe diffusion of camphorquinone (CQ) in a polystyrene (PS)/poly(2,6-dimet hyl-1,4-phenyleneoxide) (PPO) blend is studied by using the laser-induced h olographic grating relaxation technique. The probe diffusion coefficient is measured as a function of temperature and composition. Above the glass tra nsition temperature, the temperature dependence of the diffusion coefficien t fits well to the Vogel-Fulcher equation. At a fixed temperature above T-g , it is found that the logarithm of the probe diffusion coefficient varies linearly with the weight fraction of PS or PPO.