The location of both upper and lower critical phase boundaries in a polystyrene-poly(vinyl methyl ether) blend

A method has been developed for the location of both upper and lower critical cloudpoint curves in miscible polymer blends. Ternary, solvent (1)/polymer (2)/ polymer (3) systems have been used and the phase separation temperatures have been measured in solutions containing a fixed ratio of the two polymers. Extrapolation to zero solvent then gives the critical temperatures for the blend. By measuring these for several blend compositions a miscibility range can be established for a quasi-binary blend of components with specific molecular weights. Using this method, both upper and lower critical temperatures have been established for a polystyrene-poly(vinyl methyl ether) mixture.