Effect of cosolvent on the phase behavior of binary and ternary mixture for the poly(2-dimethylaminoethyl methacrylate) in supercritical solvents

• Phase behaviors for the P(2-DMAEMA) + solvents systems were measured by static method.
• Cloud-point behaviors for the P(2-DMAEMA) + solvent + cosolvent systems were measured at up to 230 MPa and to 463 K.
• (P, x) isotherms of CO2 + 2-DMAEMA system is obtained at 313.2–393.2 K and up to 19.07 MPa.
• Experimental result of CO2 + 2-DMAEMA system is correlated using P-R EOS.

Cloud-point behaviors at pressure up to 230 MPa and temperatures up to 463 K were measured for poly(2-dimethylaminoethyl methacrylate) [P(2-DMAEMA)] in CO2 (carbon dioxide), C3H8 (propane), C3H6 (propylene), C4H10 (butane), C4H8 (1-butene), and CH3OCH3 [dimethyl ether (DME)], as well as for the P(2-DMAEMA) + 2-dimethylaminiethyl methacrylate (2-DMAEMA) (or DME) in supercritical CO2. The phase behavior for the P(2-DMAEMA) + CO2 + 2-DMAEMA mixture was measured in changes of the pressure–temperature (p, T) slope and with 2-DMAEMA mass fraction of 0.0 wt%, 5.5 wt%, 11.6 wt%, 21.2 wt% and 48.1 wt%. With 51.4 wt% and 60.4 wt% 2-DMAEMA to the P(2-DMAEMA) + CO2 solution, the cloud point curves take on the appearance of a typical lower critical solution temperature (LCST) boundary, liquid + liquid transition and liquid + vapor transition. The cloud point curves for the P(2-DMAEMA) + CO2 + (0.0–95.0) wt% DME systems change the (p, T) curve from upper critical solution temperature region to lower critical solution temperature region as the DME mass fraction increases. The phase behavior curves for P(2-DMAEMA) in alkane hydrocarbons were about 50–60 K higher than P(2-DMAEMA) + alkene hydrocarbons curves, at a fixed pressure of about 70.0 MPa. Also, the impact by 2-DMAEMA and DME mass fraction for the P(2-DMAEMA) + propane + 2-DMAEMA + DME system was measured at temperatures to about 453 K and a pressure range of 4.3–192.9 MPa.The experimental data was presented for the CO2 + 2-DMAEMA system at temperatures ranging from 313.2 to 393.2 K and pressures up to 19.07 MPa. The CO2 + 2-DMAEMA system exhibits type-I phase behavior with a continuous critical mixture curve and was correlated with Peng–Robinson equation of state using a van der Waals one-fluid mixing rule including two adjustable parameters. The property of 2-DMAEMA was obtained by Constantinou-Gani group contribution method.

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