Cosolvency effects on copolymer solutions at high pressure

Abstract

Cloud‐point data to 180°C and 2800 bar are presented for polyethylene, poly(methyl acrylate), and two poly(ethylene‐co‐methyl acrylate) copolymers (10 and 31 mol % methyl acrylate) in propane and chlorodifluoromethane with two cosolvents, acetone and ethanol. The addition of small amounts of either cosolvent to the copolymer–solvent mixtures shifts the cloud‐point curve to lower pressures and temperatures, as both cosolvents provide favorable polar interactions with the acrylate group in the backbone of the copolymer. Ethanol has a larger effect than acetone since ethanol hydrogen bonds to the acrylate group. However, if the concentration of ethanol is increased above ca. 10 wt %, it self‐associates and reverts to antisolvent behavior, forcing the copolymer out of solution. For nonpolar polyethylene–propane mixtures, the polar cosolvents behave as traditional an‐tisolvents. In poly(methyl acrylate)–chlorodifluoromethane mixtures, both polar cosolvents enlarge the single‐phase region. The cloud‐point curves for the (co)polymer–propane–acetone mixtures are modeled reasonably well using the Sanchez–Lacombe equation of state with two adjustable mixture parameters. No attempt is made to model the mixtures that exhibit hydrogen bonding. © 1993 John Wiley & Sons, Inc.

Effect of the octadecyl acrylate concentration on the phase behavior of poly(octadecyl acrylate)/supercritical CO2 and C2H4 at high pressures

“…5 The highpressure polymer-SCF solvent-cosolvent studies reported in the literature show that cloud points monotonically decrease in pressure and temperature with the addition of a polar cosolvent as long as the cosolvent does not form a complex with the polar repeat units in the polymer. [6][7][8] In these cases, the cosolvency effect is directly related to the polar forces of attraction contributed by the cosolvent and to the increase in solvent density resulting from the addition of a liquid cosolvent to a supercritical fluid solvent.…”

Cloud‐Point Pressure Curves of Ethene/Poly[ethylene‐co‐((meth)acrylic acid)] Mixtures

“…The phase behavior of the monomer/polymer system needs to be known to ensure that polymerization takes place in an homogeneous fluid phase and in order to optimize separation processes after reaction. Cloud‐point pressure (CPP) curves for a series of E/poly[E‐ co ‐(acrylic acid alkyl ester)] systems, in particular for E/poly[E‐ co ‐(methyl acrylate)] (E/poly(E‐ co ‐MA)), E/poly[E‐ co ‐(butyl acrylate)] (E/poly(E‐ co ‐BA)), and E/poly[E‐ co ‐(ethylhexyl acrylate)] (E/poly(E‐ co ‐EHA)) have been determined chiefly by McHugh and coworkers,1–5 but also by other groups 6–8. With E/poly(E‐ co ‐BA) and E/poly(E‐ co ‐EHA), upon increasing the content of polar comonomer units within the polymer, the cloud‐point pressure is continuously lowered as compared to the E/polyethylene (PE) system.…”

Phase behavior of the poly(neopentyl methacrylate)+supercritical fluid solvents+neopentyl methacrylate system and CO2+neopentyl methacrylate mixtures at high pressure

“…Interpreting the effect of a cosolvent added to a supercritical solvent is slightly complicated since increasing the pressure of the system reduces the free-volume difference between the polymer and the solvent, and it increases the probability of interaction between polymer, solvent, and cosolvent in mixture [10]. The polymer þ supercritical solvent þ cosolvent studies at high pressure reported in the literature show that cloud points monotonically decrease pressure and temperature with the addition of a cosolvent as long as the cosolvent does not form a complex with the polar repeat units in the polymer [9,11]. In these cases, cosolvent effect is directly related to the polar forces of attraction contributed by the cosolvent and to the increase in solvent density resulting from the addition of a liquid cosolvent to a supercritical fluid solvent.…”