Lower Critical Solution Temperature Region Research Articles

Synthesis of Poly[N‐(2‐((3‐Morpholino‐3‐Oxopropyl)Thio)Ethyl)Methacrylamide]: A New Thermoresponsive Polymer with Tunable LCST‐ and UCST‐Type Phase Transition in Aqueous and Alcoholic Solutions

AbstractA novel monomer, N‐(2‐((3‐morpholine‐3‐isopropyl)thio)ethyl)methacrylamide (MTMA), is synthesized and polymerized by reversible addition‐fragmentation chain transfer (RAFT) polymerization to give a thermoresponsive polymer poly[N‐(2‐((3‐morpholino‐3‐oxopropyl)thio)ethyl)methacrylamide] (PMTMA). PMTMA exhibits reversible thermoresponsive phase transitions of the lower critical solution temperature (LCST) type in water and the upper critical solution temperature (UCST) type in ethanol and methanol. The degree of polymerization and concentration of PMTMA, and solvent type have a significant influence on the transition temperature. PMTMA shows complicated thermoresponse in water–alcohol mixtures. In water–ethanol mixtures, the phase diagram of PMTMA can be divided into three regions according to ethanol volume percentages, φ: 0 ≤ φ < 15% for an LCST region; 15% ≤ φ < 91.5% for a complete dissolution region; 91.5% ≤ φ ≤ 100% for a UCST region. At high water content, the LCST increases with increasing ethanol content; and at high ethanol content, the UCST decreases with increasing water content. In water–methanol mixtures, PMTMA shows more complex thermoresponse. In the range of 0–50 °C, the phase diagram can be divided into five regions, depending on the methanol volume percentages φ: 0 ≤ φ < 15% for LCST region; 15% ≤ φ < 25% for immiscible region; 25% ≤ φ < 85% for UCST region; 85% ≤ φ < 95% for fully dissolved region; 95% ≤ φ ≤ 100% for another UCST region.

Phase Behavior for the Poly(phenyl methacrylate) and Phenyl Methacrylate in Supercritical Carbon Dioxide and Dimethyl Ether

Experimental data up to 463.1 K and 269.14 MPa are revealed for binary and ternary mixtures of poly(phenyl methacrylate) [P(PhMA)] + carbon dioxide (CO2) + phenyl methacrylate (PhMA) and P(PhMA) + CO2 + dimethyl ether (DME) systems. The cloud-point pressure for the P(PhMA) + CO2 + PhMA system is measured with the variations of temperature, and PhMA weight fraction of 39.4, 45.8, 54.2, 59.9, and 62.1 wt %. In 62.1 wt % PhMA to the solution of P(PhMA) + carbon dioxide, the cloud-point phase behaviors are shown the typical lower critical solution temperature (LCST). In addition, the effect by cosolvents concentration for the P(PhMA) + CO2 + DME system is investigated at temperature to 453.9 K and pressure range from 52.24 to 80.86 MPa. The cloud point curve for P(PhMA) + CO2 + DME systems is shifted from LCST region to upper critical solution temperature (UCST) region according to the increase of DME concentration. We report experimental data of the PhMA + CO2 system at high pressures range from 6.24 to 24.9...

Phase behavior and characterization of the poly(methyl methacrylate-co-octafluoropentyl methacrylate) [P(MMA-co-OFPMA)] by supercritical dispersion polymerization

Various industries have been moving away from the use of organic solvents because of environmental regulations on safety hazards. To reduce the consumption of organic solvent to the minimum, a number of studies have been carried out using supercritical carbon dioxide (scCO2) as reaction medium to synthesize a variety of polymers in a heterogeneous reaction system. In this study, poly(methyl methacrylate-co-2,2,3,3,4,4,5,5-octafluoropentyl methacrylate) [P(MMA-co-OFPMA)] as a fluoric copolymer was prepared using supercritical dispersion polymerization in scCO2. The characterization for the prepared P(MMA-co-OFPMA) was investigated using the particle size and shape, the molecular weight (Mw), and thermal analysis. In addition, Pressure isotherms for phase behavior of binary and ternary systems between P(MMA-co-OFPMA) and association liquid fluid as well as the influence of quality of association solvents, weight average molecular weight (Mw), and cosolvents were measured.The experimental data of high pressure phase behavior for the P(MMA-co-OFPMA) in supercritical CHF3, CH2F2 and CHClF2 are presented for binary and ternary mixtures at temperatures ranging from 334K to 454K and pressures up to 194MPa. Changes of the pressure–temperature (p–T) slope of cloud–point curves for the P(MMA-co-OFPMA) [25:1]+CH2F2+methyl methacrylate (MMA) (or CHClF2) systems were measured and compared, along with cosolvents MMA (or CHClF2) mass fraction of 0.0∼30.0wt%. The phase behavior data for the P(MMA-co-OFPMA)+CH2F2+0.0∼95.0wt% CHClF2 systems are reported as a change in the p–T curve from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region as the CHClF2 mass fraction increases. The cloud–point curves for the P(MMA-co-OFPMA)+CHF3 and +CHClF2 mixtures were measured for a LCST region accordingly as the AIBN (1.0, 2.0, 3.0 and 4.0wt%) and mole ratio (MMA:OFPMA=20:1, 22:1, 25:1 and 30:1) increases.

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

Cloud-point behaviors at pressure up to 230MPa and temperatures up to 463K 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 50–60K higher than P(2-DMAEMA)+alkene hydrocarbons curves, at a fixed pressure of about 70.0MPa. 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 453K and a pressure range of 4.3–192.9MPa.The experimental data was presented for the CO2+2-DMAEMA system at temperatures ranging from 313.2 to 393.2K and pressures up to 19.07MPa. 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.

Phase behavior for the poly[2-(2-ethoxyethoxy)ethyl acrylate] and 2-(2-ethoxyethoxy)ethyl acrylate in supercritical solvents

Pressure-composition (p, x) isotherms were obtained for the carbon dioxide+2-(2-ethoxyethoxy)ethyl acrylate [2-(2-EE)EA] system at five temperatures (313.2K, 333.2K, 353.2K, 373.2K, and 393.2K) and pressure up to 22.86MPa. The carbon dioxide+2-(2-EE)EA system exhibits type-I phase behavior with a continuous mixture critical curve. The experimental results for carbon dioxide+2-(2-EE)EA mixtures are correlated using the Peng–Robinson equation of state (PR-EOS) using mixing rule including two adjustable parameters. The critical property of 2-(2-EE)EA is estimated with the Joback–Lyderson method.Experimental data up to 485K and 206.6MPa are reported for binary and ternary mixtures of poly(2-(2-ethoxyethoxy)ethyl acrylate) [P(2-(2-EE)EA)]+carbon dioxide+2-(2-EE)EA, P(2-(2-EE)EA)+carbon dioxide+dimethyl ether (DME), P(2-(2-EE)EA)+carbon dioxide+propylene and P(2-(2-EE)EA)+carbon dioxide+1-butene systems. High-pressure cloud-point data are also reported for P(2-(2-EE)EA) in supercritical carbon dioxide, propane, propylene, butane, 1-butene, and DME at temperature to 474K and a pressure range of (8.45–206.6)MPa. Cloud-point behavior for the P(2-(2-EE)EA)+carbon dioxide+2-(2-EE)EA system were measured in changes of the pressure–temperature (p, T) slope and with 2-(2-EE)EA mass fraction of 0.0wt%, 5.9wt%, 14.9wt%, 30.3wt% and 60.2wt%. With 0.650 2-(2-EE)EA to the P(2-(2-EE)EA)+carbon dioxide solution, the cloud point curves take on the appearance of a typical lower critical solution temperature boundary. The P(2-(2-EE)EA)+carbon dioxide+(0.0–46.6)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. Also, the impact by propylene and 1-butene mass fraction for the P(2-(2-EE)EA)+carbon dioxide+propylene and 1-butene system is measured at temperatures to 454K and a pressure range of (75.7 to 119.6)MPa.

Thermo and pH responsive water soluble polythiophene graft copolymer showing logic operation and nitroaromatic sensing

A polythiophene based water soluble thermo and pH responsive graft copolymer is prepared by anchoring the initiator moiety (2-bromoisobutyryl bromide) on 3-thiophene ethanol and polymerizing using ferric chloride to produce the 2,5-poly(3-[1-ethyl-2-(2-bromoisobutyrate)]) thiophene macroinitiator (PTI), followed by polymerization with a mixture of varying composition of diethyleneglycol methylether methacrylate (MeO2MA) and N,N-dimethyl aminoethyl methacrylate (DMAEMA) at 30 °C using copper based atom transfer radical polymerization (ATRP). The polymers are characterized by gel permeation chromatography (GPC) and by 1H NMR spectroscopy. Polythiophene-g-P(MeO2MA-co-DMAEMA) (PTDM) exhibits considerable water solubility but due to the lower critical solution temperature (LCST) of aqueous PMeO2MA at ∼26 °C the particle sizes observed by dynamic light scattering (DLS) show a sharp increase in the region 25–30 °C only for a pH value of 9.2. However, at lower pH values (pH 4 or 7), in the LCST region of PMeO2MA there is no increase of particle size. The TEM micrographs of PTDM indicate core–shell morphology at pH4 and pH7 with a gradual decreasing of the size (with PT at the core and P(MeO2MA-co-DMAEMA) at the shell), and at pH 9.2 no core–shell morphology is observed due to the absence of protonation at the –NMe2 groups of the PDMAEMA segments. The fluorescence intensity of the PTDM solution at pH 9.2 also shows a sharp increase in the temperature range 22–29 °C, but remains almost without change at pH 4 and 7. Using the pH and temperature as inputs and the fluorescence intensity as an output, the system functions as a fully polymeric AND logic gate, and this is the first report using polythiophene as the fluorescence probe. Also PTDM in the solid/solution state exhibits considerable quenching of fluorescence intensities in the presence of nitroaromatics such as picric acid, dinitro phenol, etc. and may be used for sensing nitroaromatics.

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

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.

One-pot synthesis of thermal responsive QDs–PNIPAM hybrid fluorescent microspheres by controlling the polymerization temperature at two different polymerization stages

In the present study, for the first time, without the help of any amphiphilic polymers or polymerizable surfactants, 3-mercaptopropionic acid (MPA) capped CdTe quantum dots (QDs) could be one-pot copolymerized into poly(N-isopropylacrylamide) (PNIPAM) microspheres during the monomer polymerization process just by controlling the synthesis temperature at two different polymerization stages. In the first stage, NIPAM monomers were initiated by potassium persulfate (KPS) below the lower critical solution temperature (LCST) to form PNIPAM networks with CdTe QDs distributed throughout. In the second stage, when the polymerize temperature was raised above the LCST, the PNIPAM networks collapsed to form spheres and the CdTe QDs were entrapped into the PNIPAM microspheres (denoted as CdTe–PNIPAM microspheres). Transmission electron microscopy (TEM) images showed that CdTe QDs have been successfully entrapped within the PNIPAM matrix. According to the dynamic light scattering (DLS) results, the CdTe–PNIPAM hybrid microspheres had a significantly narrow size distribution and their mean hydrodynamic diameter was about 267 nm. Compared with the original CdTe QDs, the CdTe–PNIPAM microspheres exhibited not only a prominent red-shift of their emission wavelength (as much as 36 nm), but also temperature dependent on–off fluorescence properties. Around the LCST, when the temperature was increasing, the fluorescence intensity decreased sharply; when cooling the solution, the fluorescence intensity would restore. Moreover, after repeated heating and cooling cycles, the photoluminescence (PL) quenching and enhancement processes were fully reversible around the LCST region.

Novel sodium alginate-poly( N-isopropylacrylamide) semi-interpenetrating polymer network membranes for pervaporation separation of water + ethanol mixtures

Novel semi-interpenetrating polymer network (semi-IPN) membranes of sodium alginate (NaAlg) and thermoresponsive poly( N-isopropylacrylamide) (PNIPAAm) were prepared by free radical polymerization using potassium persulfate as an initiator. Membranes were crosslinked with glutaraldehyde and used in pervaporation (PV) separation of water–ethanol mixtures at varying feed compositions and temperatures. Membranes were characterized by Fourier transform infrared spectroscopy (FTIR) to assess intermolecular interactions. Thermogravimetry (TGA) was used to study their thermal stability. PV separation characteristics of the membranes showed a dependence on thermosensitive nature of NIPAAm. Increasing the NIPAAm content of the semi-IPN network resulted in an increased selectivity with a decreased permeation flux. The membrane containing 30 wt.% NIPAAm showed the highest selectivity of 18,881 with a flux of 0.137 kg/m 2 h at 40 °C, i.e., the above lower critical solution temperature (LCST) of NIPAAm, but below its LCST, i.e., at 25 °C, it exhibited considerably a lower selectivity of 92 with a flux of 0.185 kg/m 2 h for 15 wt.% water containing feed. Selectivity decreased with decreasing temperature at 15 wt.% water in the feed mixture below the LCST region, i.e., at 30 °C due to increase in the membrane pore size, thereby affecting the membrane selectivity with a considerable increase in flux of up to 0.225 kg/m 2 h. The reported membranes are of the first kind in the membrane literature, wherein a thermoresponsive NIPAAm polymer is used with a hydrophilic NaAlg polymer to form the semi-IPN membrane for PV dehydration of ethanol.

Phase Behavior for Mixtures of Poly(2-ethylhexyl acrylate) + 2-Ethylhexyl Acrylate and Poly(2-ethylhexyl methacrylate) + 2-Ethylhexyl Methacrylate with Supercritical Fluid Solvents

Experimental cloud-point data up to 478 K and 248.0 MPa are reported for binary and ternary mixtures of poly(2-ethylhexyl methacrylate) (1) + carbon dioxide (2) + 2-ethylhexyl methacrylate (3) and poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) + 2-ethylhexyl acrylate (3) systems. High-pressure cloud-point data are also reported for poly(2-ethylhexyl methacrylate) and poly(2-ethylhexyl acrylate) in supercritical propane, propylene, butane, 1-butene, and dimethyl ether. Cloud-point behavior for the poly(2-ethylhexyl methacrylate) (1) + carbon dioxide (2) + 2-ethylhexyl methacrylate (3) system were measured in changes of the pressure, temperature (p, T) slope and with 2-ethylhexyl methacrylate mass fraction of w3 = 0.0, 0.201, 0.303, and 0.564. With w3 = 0.666 2-ethylhexyl methacrylate to the poly(2-ethylhexyl methacrylate) (1) + carbon dioxide (2) solution, the cloud-point curves take on the appearance of a typical lower critical solution temperature boundary. The poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) + w3 = 0.0, 0.097, 0.206, 0.409, 0.552, and 0.604 2-ethylhexyl acrylate (3) systems change the (p, T) curve from upper critical solution temperature region to lower critical solution temperature region as the 2-ethylhexyl acrylate mass fraction increases. For w3 = 0.709 2-ethylhexyl acrylate, the poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) solution significantly changes the phase behavior. Also, the impact by dimethyl ether mass fraction for the poly(2-ethylhexyl methacrylate) (1) and poly(2-ethylhexyl acrylate) (1) + carbon dioxide (2) + dimethyl ether (3) system is measured at temperatures to 455 K and a pressure range of (4.3 to 248.0) MPa. Pressure, composition (p, x) isotherms are obtained for the carbon dioxide (1) + 2-ethylhexyl methacrylate (2) systems at (313.15, 333.15, 353.15, 373.15, and 393.15) K and pressure up to 20.5 MPa. The carbon dioxide (1) + 2-ethylhexyl methacrylate (2) systems exhibit type-I phase behavior with a continuous mixture critical curve. The experimental results for carbon dioxide (1) + 2-ethylhexyl methacrylate (2) mixtures are modeled using the Peng−Robinson equation of state with two adjustable parameters.

Phase Behavior of Binary and Ternary Mixtures of Poly(decyl acrylate)−Supercritical Solvents−Decyl Acrylate and Poly(decyl methacrylate)−CO2−Decyl Methacrylate Systems

Experimental cloud-point data up to 205 °C and 2300 bar are measured for binary and ternary mixtures of poly(decyl acrylate) [poly(DA)]−supercritical solvents−decyl acrylate (DA) and poly(decyl methacrylate) [poly(DMA)]−CO2−decyl methacrylate (DMA). Also, the cloud-point curves show the binary mixtures for poly(DA) in supercritical CO2, propane, propylene, butane, 1-butene, and dimethyl ether (DME). The phase behaviors for the poly(DMA)−CO2−DMA system are measured in changes of the pressure−temperature (P−T) slope and with DMA concentrations of 4.4, 6.7, 11.2, 22.8, and 32.9 wt %. Adding 41.6 wt % DMA to the poly(DMA)−CO2 solution significantly changes the phase behavior; the curves take on the appearance of a typical LCST boundary. The cloud-point curves for the poly(DA)−CO2 system with 0, 7.5, 14.9, 23.4, and 34.9 wt % DA changes the P−T curve from an upper critical solution temperature (UCST) region to a lower critical solution temperature (LCST) region as the decyl acrylate concentration increases. Adding 40.2 wt % DA to the poly(DA)−CO2 solution significantly changes the phase behavior. The cloud-point curve takes on the appearance of a typical lower LCST region. High-pressure phase behavior data are obtained for the CO2−DA and CO2−DMA systems at temperatures in the range 40−120 °C and pressures up to 189 bar. The CO2−DA and CO2−DMA systems exhibit type-I phase behavior with a continuous mixture-critical curve. The experimental results for the CO2−DA and CO2−DMA mixtures are modeled using the Peng−Robinson equation of state. A good fit of the data is obtained from the Peng−Robinson equation of state using two adjustable parameters for CO2−DA and CO2−DMA systems.

Solubility in the binary and ternary system for poly(alkyl acrylate)-supercritical solvent mixtures

Experimental cloud-point data to 210 ‡C and 2,200 bar are presented for binary and ternary mixtures of poly(methyl acrylate)-CO2-methy acrylate and poly(ethyl acrylate)-CO2, propylene, and 1-butene-ethyl aerylate systems. The accuracy of the experimental apparatus was tested by comparing the measured pressure-temperature phase behavior data of the poly(ethyl acrylate)-CO2 system obtained in this study with those of Rindfleisch et al. [1995]. The phase behaviors for the system poly(methyl acrylate)-CO2-methyl acrylate were measured in changes of pressure-temperature slope, and with cosolvent concentrations of 0, 5.0, 13.7, 25.3, and 43.3 wt%, respectively. With 48.3 wt% methyl acrylate to the poly(methyl acrylate)-CO2 solution significantly changes, the phase behavior curve takes on the appearance of a typical lower critical solution temperature (LCST) boundary. The impact of ethyl acrylate on the cloud-point for the poly(ethyl acrylate)-CO2 system shows the change of slope of the phase behavior curves from negative to positive with ethyl acrylate concentration of 0, 8.2, and 25.0 wt%. The cloud-point behavior for the poly(ethyl acrylate)-CO2-39.5 wt% ethyl acrylate system shows an LCST curve. The solubility curve to ∼150 ‡C and 1,650 bar for poly(ethyl acrylate)-propylene-ethyl acrylate system shows the change of pressure-temperature diagram and with ethyl acrylate concentration of 0, 7.2 and 21.0 wt%. Also, when 41.1 wt% ethyl acrylate was added to the poly(ethyl acrylate)-propylene solution, the phase behavior curve showed the LCST region. The high pressure phase behavior of poly(ethyl acrylate)-1-butene-0, 3.1, 8.1, 18.5 and 30.7 wt% ethyl acrylate system presented the change of pressure-temperature curve from the UCST region to U-LCST region as the ethyl acrylate concentration increased.

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

Pressure–composition isotherms were measured for the CO2/octadecyl acrylate system at 45.0, 80.0, and 100.0°C and at pressures up to 307 bar. This system exhibited type I phase behavior with a continuous mixture-critical curve. The solubility of octadecyl acrylate for the CO2/octadecyl acrylate system increased as the temperature increased at a constant pressure. The experimental results for the CO2/octadecyl acrylate system were modeled with the Peng–Robinson equation of state. A good fit of the data was obtained with the Peng–Robinson equation of state with one adjustable parameter for the CO2/octadecyl acrylate system. Experimental cloud-point data for the poly(octadecyl acrylate)/CO2/octadecyl acrylate system were measured from 36 to 193°C and at pressures up to 2100 bar, and the added octadecyl acrylate concentrations were 11.9, 25.9, 28.0, 35.0, and 40.0 wt %. Poly(octadecyl acrylate) dissolved in pure CO2 up to 250°C and 2100 bar. Also, adding 45.0 wt % octadecyl acrylate to the poly(octadecyl acrylate)/CO2 solution significantly changed the phase behavior. This system changed the pressure–temperature slope of the phase-behavior curves from an upper critical solution temperature (UCST) region to a lower critical solution temperature region as the octadecyl acrylate concentration increased. Cloud-point data to 150°C and 750 bar were examined for poly(octadecyl acrylate)/C2H4/octadecyl acrylate mixtures at octadecyl acrylate concentrations of 0.0, 15.0, and 45.0 wt %. The cloud-point curve of the poly(octadecyl acrylate)/C2H4 system was relatively flat at 730 bar between 41 and 150°C. The cloud-point curves of 15.0 and 45.0 wt % octadecyl acrylate exhibited positive slopes extending to 35°C and approximately 180 bar. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 372–380, 2002

Monomer concentration effect on the phase behavior of poly(propyl acrylate) and poly(propyl methacrylate) with supercritical CO2 and C2H4

Experimental cloud-point data to temperature of 186 °C and pressure of ~2,500 bar are presented for ternary mixtures of poly(propyl acrylate)(PPA)-CO2-propyl acrylate (PA) PPA-C2H4-PA and poly(propyl methacrylate) (PPMA)-CO2-propyl methacrylate (PMA) systems. Cloud-point pressures of PPA-CO2-PA system were measured in the temperature range of 32 °C to 175 dgC and to pressures as high as 2,070 bar with PA concentrations of 0.0, 5.0, 11.7 and 30.4 wt%. Adding 34.1 wt% PA to the PPA-CO2 mixture significantly changes the phase behavior. This system changes the pressure-temperature slope of the phase behavior curves from U-LCST region to LCST region as the PA concentration increases. Cloud-point data to 170 °C and 1,400 bar are presented for PPA-C2H4-PA mixtures and with PA concentration of 0.0, 5.7, 15.5 and 22.2 wt%. The cloud-point curve of PPA-C2H4 system shows relatively flat at 730 bar for temperatures between 41 and 150 °C. With 15.5 and 22.2 wt% PA the cloud-point curve exhibits a positive slope that extends to 35 °C and ~180 bar. Also, the ternary PPMA-CO2-PMA system was measured below 186 °C and 2,484 bar, and with cosolvent of 5.2-20.1 wt%. PPMA does not dissolve in pure CO2 to 233 °C and 2,500 bar. Also, when 41.5 wt% PMA is added to the PPMA-CO2 solution, the cloud-point curve shows the typical appearance of a lower critical solution temperature (LCST) boundary.

Diffusion of gases in polymer blends near the lower critical solution temperature

AbstractGas diffusion through miscible blends of polystyrene (PS) with poly(vinyl methyl ether) (PVME) and poly(styrene‐stat‐acrylonitrile) (PSAN) with poly(methyl methacrylate) (PMMA) is studied from temperatures below the corresponding lower critical solution temperature (LCST) to temperatures above. The Arrhenius equation describes the temperature dependence of diffusion coefficients of pure components. Diffusion coefficients of methane in the 20/80 PS/PVME blend also follow the Arrhenius equation in the temperature ranges above and below their corresponding LCST; however, discontinuity is observed in the LCST region. In contrast to the PS/PVME blend, discontinuity in the LCST region is not obvious for nitrogen and methane in the 50/50 PSAN/PMMA blend. These phenomena are discussed in terms of free volume and morphology changes in the LCST region.