Ionomer glasses of generic composition SiO2-Al2O3-P2O5-CaO-CaF2 were studied using differential scanning calorimetry (DSC) and high temperature dynamic-mechanical thermal analysis (DMTA). High temperature DMTA was used to measure the glass transition temperatures (T-g) of the original starting glass compositions, as well as being able to follow amorphous phase separation (APS) within the glass. High temperature DMTA traces of all the glasses studied exhibited two maxima in tan delta. These maxima correspond to two glass transition temperatures and demonstrate that amorphous phase separation of the parent glass into two glass phases had occurred. A DMTA study of a Sodium-Boro-Silicate glass, which is known to undergo amorphous phase separation yielded similar results. DSC studies showed that the ionomer glasses underwent a nucleation process at temperatures just above the glass transition temperature which is probably associated with APS. The glasses exhibited optimum nucleation temperatures which moved to lower temperatures with longer hold times indicating the time dependency of the APS process.