Component effects in phase separation of polymer‐polymer‐solvent systems

The nature of phase separation in polymer‐polymer‐solvent systems was investigated. Threshold concentrations necessary for the separation of polystyrene and poly(methyl methacrylate) in a variety of solvents were determined. Only a rough correlation between cohesive energy densities and solvent compatibilizing powers was found. Separation data for combinations of a number of substituted polystyrenes were determined in reference solvents. The general occurrence of phase separation in these systems is thought to stem from the unique array of functional groups presented by a polymer molecule to its environment. Phase separation in conjunction with available heats of mixing indicate the exothermic heat of mixing chlorobenzene and toluene is due to interaction of the chloro group with an aromatic ring. Changes in chain extension and solvation as a function of temperature were detected by means of phase separation.