Prediction and experimental verification on blend phase diagrams of two structurally isomeric polymers: Poly(4-methylstyrene) and poly(α-methylstyrene)

The phase behavior of blends comprising two isomeric polymers, poly(4-methylstyrene) (P4MS) and poly(α-methylstyrene) (PαMS), was analyzed. Both model prediction and experimental confirmation were conducted. At low PαMS molecular weights, the polymer blends were miscible with the lower critical solution temperature (LCST) at about 140 °C. A model based on a modified Flory-Huggins interaction expression was then developed using the experimental phase diagram of miscible blends comprising low molecular weight constituents. At higher molecular weights, the P4MS/PαMS mixtures became immiscible.