Effect of cosolvent on cloud-point of binary and ternary systems for the poly(4-chlorostyrene) + cosolvent mixtures in supercritical fluid solvents

Abstract

Pressure-composition (P–x) isotherms were obtained for the carbon dioxide+4-chlorostyrene (4-CS) system using static apparatus at five temperatures (313.2, 333.2, 353.2, 373.2 and 393.2K) and pressure up to 23.74MPa. The experimental results for the carbon dioxide+4-CS system were modeled with the Peng–Robinson equation of state (PR EOS) using two adjustable parameters. The comparison between the experimental results and the calculated curves shows a good agreement at five temperatures. Three phases were not observed at any five temperatures in this system.The experiments were conducted to obtain cloud-point data of binary and ternary mixture for the poly(4-chlorostyrene) [P(4-CS), Mw=87,000, Mn=57,000, polydispersity=1.53]+supercritical solvents (propane, propylene, butane and 1-butene)+acetone, the P(4-CS)+supercritical solvents [butane, 1-butene and dimethyl ether (DME)]+4-CS and the P(4-CS)+supercritical solvents (butane and 1-butene)+ethanol, the P(4-CS)+supercritical solvents (propylene, 1-butene and DME) and the P(4-CS)+carbon dioxide+DME systems. High pressure phase behavior experiment for the binary and ternary mixture of the P(4-CS)+supercritical solvents+cosolvent systems is measured within a temperatures range of 332.8–494.2K and pressure up to ca. 260.0MPa. The P(4-CS)+supercritical solvents (propane, propylene and 1-butene)+acetone systems show the changes in the pressure–temperature (p–T) curve from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region as acetone concentration increases. The phase behavior curves for the P(4-CS)+supercritical solvents (butane, 1-butene)+4-CS systems of three systems [the P(4-CS)+4-CS mixture in supercritical solvents (butane, 1-butene and DME)] exhibit UCST region with negative slopes, but in the case of the P(4-CS)+DME+4-CS system, cloud-point behavior shows LCST-type curve with a positive slope. The cloud-point behaviors for P(4-CS)+supercritical solvents (butane and 1-butene)+ethanol systems exhibit USCT-type curves with negative slopes. The P(4-CS)+carbon dioxide+xwt.% DME system shows cloud-point curves changing from UCST region to LCST region as DME concentration increases.