Low-molecular-weight polystyrene was nitrated to different levels. The nitrated polystyrene was blended with different molecular weights of poly(acrylic acid), PAA. The glass transition temperatures (T-g) for the mixtures were investigated by differential scanning calorimetry. A single T-g was observed for all blends, indicating single-phase blends. In general, It was found that the T-g increases with molecular weight of PAA. The T-g values of the blends showed a positive deviation from the linear average T-g as a result of strong hydrogen bonding between the segments of the component polymers. The observed T-g values were not adequately represented by simple predictive equations or by single-parameter fitting equations. However, two-parameter fitting equations gave a reasonable representation of the data.