The dynamic mechanical properties of polystyrene/ethyl benzene, polymethyl methacrylate/water, polyethyl methacrylate/ethyl hexyl adipate, and poly-2-hydroxyethyl methacrylate/water were studied between 10 and 100°K. A free-decay resonance acoustic spectrometer was designed for this purpose. It was found that the presence of diluents causes the low-temperature loss peaks of the polyrners in question to shift to higher temperatures. This observation is compatible with the hypothesis that at very low temperatures, the diluent molecules are immobilized to occupy free space between adjacent polymer chains. The hindering action of these molecules on the kinetic motions of the side groups of the polymer thus renders greater thermal energy necessary to initiate the relaxation processes.