T$_{g}$ in Polymer/Oligomer Athermal Blends

The glass transition behavior of poly($\alpha $-methyl styrene), its tridecamer, and athermal blends with its hexamer is investigated using differential scanning calorimetry. The blends are prepared to exhibit approximately the same T$_{g}$ as the tridecamer but with varying molecular weight distributions. The glass transition of the blends is found to become broader than that of the pure materials. However, the absolute heat capacity of the blends maintains unchanged from its components indicating that the blends are athermal mixtures. The broadening of the Tg is evaluated in the context of recent models describing this behavior. In addition, we examine the ability of the TNM model to describe the rate dependence of T$_{g}$ and aging effects.