Phase separation in polymer solutions: I. Liquid-liquid phase separation of PPO poly (2, 6-dimethyl 1, 4-phenylene oxide) in binary mixtures with toluene and ternary mixtures with toluene and ethyl alcohol

In the system poly(2, 6-dimethy1-1, 4-phenylene oxide) (PPO)-toluene three phase separation lines can be detected: the melting point curve, the cloud point curve, and the spinodial. Because crystallization of PPO occurs very slowly, a phase transition will always be initiated by liquid-liquid phase separation. Depending upon the experimental circumstances two mechanisms are possible, either nucleation and growth (extremely slowly in this system) or the spinodial decomposition mechanism. In the system PPO-toluene-ethanol, liquid-liquid phase separation occurs leading to two bulk liquid fractions. Only in mixtures containing very small concentrations of alcohol can three phase separation curves be detected from which the position of the cloud point curve of the system PPO-toluene can be confirmed