Confinement and interfacial effects on the alpha relaxation dynamics of thin polymer films

It is now known that both the glass transition temperature ($T_{g})$ and the alpha relaxation dynamics can deviate substantially from the bulk with confinement of polymer films. Using a novel fluorescence multilayer method, it has been established that the deviations in $T_{g}$ observed with decreasing film thickness for polystyrene and poly(methyl methacrylate) films supported on silica is a result of interfacial effects. Since the glass transition is related to the cooperative segmental (alpha) relaxation dynamics, it must be that these dynamics at the interfaces are different from the bulk. However, because of experimental limitations no direct measurement of the complete alpha relaxation time distribution at the interfaces has been conducted. Here we present results of a novel dielectric multilayer method that allows for such measurements. Our results indicate that both the alpha relaxation time distribution and the average alpha relaxation time are affected by the interfaces for polystyrene films.