Solubility of polystyrene in liquid sulfur dioxide

The two‐phase equilibrium in the system polystyrene (PS)‐liquid sulfur dioxide [SO 2 ( l )] was investigated, mainly at room temperature. The system consisted of an upper PS‐rich phase, concentration (30–50)% depending on the way of preparation, and a lower phase containing less than 1% PS. The range of molecular weights of the PS samples used was 22,000–350,000 (M̄ w ). PS with an M̄ w value of 22,000 dissolved homogeneously in SO 2 ( l ). In systems forming two phases a fractionation of PS with respect to molecular weight was observed. The M̄ w value of the PS fraction dissolved in the lower PS lean phase was always substantially lower than that of the upper phase. When increasing the temperature to 90–95°C, the two phases disappeared and the PS component formed a jellylike mass with a very low solubility in SO 2 ( l ). Also in the supercritical dense SO 2 gas, the solubility of PS was a few tenths of a percent only. Experiments with Soxhlet extraction indicated an extractability of a few percent.