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RESEARCH PRODUCT

Temperature and pressure dependence of phase separation of trans-decahydronaphthalene/polystyrene solution

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Abstract The cloud-point temperatures (Tcl’s) of trans-decahydronaphthalene (TD)/polystyrene (PS, Mw=270 kg/mol) solutions were determined by light scattering measurements over a range of temperatures (1–16 °C), pressures (100–900 bar), and compositions (4.2–21.6 vol% polymer). The system phase separates upon cooling and the Tcl was found to increase with the rising pressure for the constant composition. In the absence of special effects this finding indicates positive excess volumes. The special attention was paid to the demixing temperatures as a function of the pressure for the different polymer solutions and the plots in the T-volume fraction plane and P-volume fraction plane. The cloud-point curves of polymer solutions under changing pressures were observed for different compositions, demonstrates that the TD/PS system exhibits UCST (phase separation upon cooling) behavior. With this data the phase diagrams under pressure were calculated applying the Sanchez–Lacombe (SL) lattice fluid theory. Furthermore, the cause of phase separation, i.e., the influence of Flory–Huggins (FH) interaction parameter under pressure was investigated. The predictions of the SL theory concerning the FH interaction parameter and the influence of pressure on miscibility are investigated. The LCSP (phase separation upon increasing pressure) and UCST behavior were predicated by extrapolating the pressure to negative region on pressure-composition plane for TD/PS polymer solutions.