Prediction of gas solubility in binary polymer+solvent mixtures

This paper is devoted to a theory of gas solubility in highly asymmetrical mixed solvents composed of a low molecular weight (such as water, alcohol, etc.) and a high molecular weight (such as polymer, protein, etc.) cosolvents. The experimental solubilities of Ar, CH₄, C₂H₆ and C₃H₈ in aqueous solutions of polypropylene glycol and polyethylene glycol were selected for comparison with the theory. The approach for predicting these solubilities is based on the Kirkwood-Buff formalism for ternary mixtures, which allowed one to derive a rigorous expression for the Henry constant in mixed solvents. Starting from this expression, the solubilities could be predicted in terms of those in each of the two constituents and the properties of the mixed solvent. This expression combined with the Flory-Huggins equation for the activity coefficient in a binary mixed solvent provided very accurate results, when the Flory-Huggins interaction parameter was used as an adjustable quantity. A simple expression in which the solubility could be predicted in terms of those in each of the two constituents and the molar volumes of the latter was also derived. While less accurate that the previous expression, it provided more than satisfactory results.     

Löslichkeiten in homologen und isomeren Reihen

Solubilities of Homologous and Isomeric Series Solubilities in water and organic solvents of homologous series of symmetrical dialkyl ketones (having no melting point alternations) and of β-phenyl,β-hydroxyl,β-alkyl-propionic acids (all with alternating melting points) were determined. In the case of medium chained dialkyl ketones the solubilities decrease in linear logarithmic proportion with increasing alkyl chain, according to the relationship of Erichsen. In isomeric series having systematically displaced substituents on n-paraffin C₂₂H₄₆, the maximum solubilities correspond to lowest melting points. In this case a quantitative relationship can not be formulated.     

Solubility parameters of poly(di-n-alkyl cyclohexyl-) and poly(di-n-alkyl phenyl itaconates)

Solubility parameters of poly(dicyclohexyl-), poly(diphenyl itaconate) and of the first three members of the poly(dialkyl cyclohexyl-) and poly(dialkyl phenylitaconate) homologous series were determined from limiting viscosity numbers in various solvents and solvent mixtures, differing in structure, polarity and composition. The values obtained are within limits of 19.0 and 16.7 (J^1/2. cm^-3/2). Phenyl groups in the substituents lead to slightly higher values than cyclohexyl rings and the introduction of alkyl groups in both series results in a progressive decrease of the solubility parameter. The experimental values are slightly lower than those obtained by calculation from molar attraction constants.     

Promoted absorption of CO at high temperature by cuprous-based ternary deep eutectic solvents

Achieving efficient dissolution of carbon monoxide (CO) in the solvent is very helpful for the implementation of carbonylation reaction at ambient pressure. However, almost all of common solvents show very low solubilities of CO at high temperature. Herein, a series of cuprous-based ternary deep eutectic solvent (DES) was prepared by mixing imidazolium hydrochloride with CuCl and ZnCl₂. The ternary DES [BimH]Cl-CuCl-1.0ZnCl₂ exhibited very large CO absorption capacity (0.075 mol mol⁻¹, 1 bar) even at a high temperature (353.2 K), which is superior to all of the reported absorbents. Moreover, the ternary DES [BimH]Cl-CuCl-1.0ZnCl₂ could further promote the reactive absorption of CO to conduct the aminocarbonylation reaction effortlessly at ambient pressure, and thus the targeted products benzamides were obtained in 70–97 yields. We believe that this finding opens a new way to design advanced solvents for efficient capture of CO at high temperature.     

The solubility of sulfur dioxide and hydrogen sulfide in associating solvents

The solubilities of SO₂ are reported in the solvents N, N-dimethyl acetamide (DMA), N, N-dimethyl formamide (DMF), ethyl acetate, acetonitrile, chlorobenzene, methanol, (1,2-ethanediol) ethylene glycol and acetone for atmospheric pressure and for temperatures ranging from 268 K to 333 K (-5°C to 60°C). Solubilities of H₂S are also reported for the first five of the above-mentioned solvents and for hexane for similar conditions. These gases and solvents exhibit extreme molecular interactions which are reflected in unusual solubility behavior. This paper is a continuing attempt in providing data and analyses for improving the understanding of gas solubilities in complex gas-solvent systems. Solubilities expressed as hydrogen-bonding factors have been found useful in systematically relating gas solubilities in one associating or reacting solvent to another chemically similar solvent. Thus, with a limited amount of data for gas solubilities, it is often possible to predict solubilities even in highly associated or reacting gas-solvent solutions.     

Solubility study for the purification of hydrogen from high pressure hydrocracker off-gas by an absorption-stripping process

Experiments were carried out to identify a solvent which has a high solubility and selectivity for methane relative to hydrogen at 295 K and pressures from 13.88 to 20.78 MPa. Binary solubilities with pure hydrogen and methane, and ternary solubilities with 73 mol% H₂ and 27 mol% CH₄ were measured at 295 K and for pressures from 6.99 to 20.78 MPa in various organic solvents. This gas mixture simulates hydrocracker and hydrotreater off-gases which are candidates for purification with an absorption-stripper. Of the solvents tested, 2,2,4-trimethylpentane (iso-octane), which showed very high methane solubility and a reasonable selectivity, and methylcyclohexane, which showed a very high selectivity and a reasonable solubility, are the best solvents for methane absorption. Correlations for hydrogen and methane as a function of pressure and solvent solubility parameter were developed with the experimental solubilities. Binary interaction parameters for Peng-Robinson (Peng and Robinson, 1976) and Soave-Redlich-Kwong (Soave, 1972) equations of state were calculated with experimental solubility results. Prediction of gas solubility in a ternary system was compared with experimental and found to be satisfactory when experimental binary interaction parameters were used.     

Viscosity slope constants for solutions of nylon 6 and polytetrahydrofuran

Measurements of the viscosity slope constant k were made on solutions of nylon 6 and polytetrahydrofuran under different conditions of temperature, solvent, and molecular weight of polymer; θ-conditions were included so that the expansion factor α could be determined in each case. The value of k was influenced somewhat by the particular equation employed to derive it, and generally the Schulz-Blaschke equation (yielding k_SB) was the most reliable. Slope constants (k_calc) calculated according to an expression of Sakai were plotted as a function of α³ and were compared with the corresponding curves in terms of experimental values of k. The agreement was moderately good for PTHF but poor in the case of nylon 6. An expression (due to Imai) involving experimental values of k and α was examined in order to establish a unique value of the slope constant k_θ under θ-conditions by an extrapolation procedure. Although individual value of k_θ for nylon 6 measured under θ-conditions were dependent on molecular weight, the Imai plot yielded a unique value of 0.50 and a slope similar in magnitude to that found for other polymer/solvent systems.     

Aggregation behavior of new cyclic saturated copolymers synthesized via ring-opening metathesis polymerization

Cyclic saturated copolymers were prepared from 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1^2,5.1^7,10]dodec-3-ene (MMT) with polar ester group and dicyclopentadiene (DCP) without polar group. This procedure consisted of ring-opening metathesis polymerization (ROMP) followed by hydrogenation. Monomer reactivity of DCP was higher than that of MMT; the monomer reactivity ratio r_DCP/r_MMT varied from 2.135 to 1.159 in a temperature range from 80 to 130 °C. These kinetic results indicated that the copolymer had distribution of DCP composition in a macromolecule chain, which could provide the interesting aggregation behavior. The aggregation behaviors of the hydrogenated copolymer and the homopolymer in various solvents were also examined using dynamic light scattering (DLS) and static light scattering (SLS). DLS analysis indicated that the fast mode in each polymer is attributed to the diffusive motion of each single polymer chain, while the slow mode in the copolymer is caused by aggregated polymer. The aggregation degree of the copolymer decreased with increasing hydrophobicity of solvent, decreasing polymer concentration, decreasing molecular size of solvent and increasing temperature. Based on these findings, the mechanism of aggregation behavior was clarified that the DCP-rich unit in a macromolecule might be acting as core to give the aggregation in poor solvent.     

Prediction of solubilities of solid solutes in carbon dioxide-expanded organic solvents using the predictive Soave–Redlich–Kwong (PSRK) equation of state

In this study, the solubilities of solid solutes in carbon dioxide (CO₂)-expanded organic solvents are predicted using the predictive Soave–Redlich–Kwong (PSRK) equation of state (EOS). The liquid-phase compositions and volume expansion ratios of CO₂-expanded organic solvents are predicted prior to the solubility predictions. With predicted liquid-phase compositions and volumetric properties, the solubilities of cholesterol in CO₂-expanded acetone, naphthalene in CO₂-expanded toluene, stearic acid in CO₂ expanded ethyl acetate and tetradecanoic acid in CO₂-expanded ethyl acetate are predicted according to their reference solubilities in pure organic solvents. In addition to satisfactory predictions of liquid-phase composition and volume expansion ratios, the PSRK EOS also provides qualitative prediction ability for solubilities of solid solutes in CO₂-expanded organic solvent. This study demonstrated that the PSRK EOS was a simple model with predictive ability for solubility evaluation in preliminary process design and development for supercritical fluid technology using CO₂-expanded organic solvents.     

Segmental motion of stereoregular poly(methyl methacrylates) in a homologous series of n-alkyl acetate solvents by nmr relaxation measurements

The ¹³C spin-lattice relaxation times, T₁s, of both stereoregular poly(methyl methacrylates) (PMMA) and homologous series of n-alkyl acetate solvents in solution have been measured at 40°C. It was observed that the motion of polar side-chains was highly affected by the degree of interaction with solvent molecules. The stronger polymer-solvent interactions in predominantly syndiotactic PMMA solutions than in isotactic PMMA solutions were shown from the T₁ values for the carbonyl, methoxy, and quaternary carbons in polymer segments and also from the carbonyl T₁s of solvent molecules. By relating the solvent dependences of the T₁ data in syndiotactic polymer solutions to that of the known dissolution rate data of atactic PMMA, it was found that the solvent dependences of the T₁ values of those carbon groups in which the polymer-solvent interaction is not significant, e.g., methylene and α-methyl carbon groups, were consistent with the solvent dependence of the dissolution rate of polymer. This result suggested that the dissolution of polymer is mainly governed not by the sorption process related to the polymer-solvent interaction but by the transport process related to the local motions of polymer segments and solvent molecules.     

Solvent effect on the lower critical solution temperature of biodegradable thermosensitive poly(organophosphazenes)

Summary The solvent effect on the lower critical solution temperature (LCST) of poly(organophosphazenes) with methoxy-poly(ethylene glycol) (MPEG) and amino acid esters as side groups was examined in terms of the structure of polyphosphazenes in aqueous solutions containing one of the organic solvents selected from monoalcohols, ethylene glycol derivatives, alkylamines, and other common solvents. When such a solvent was added to the aqueous solutions of the polymers, their LCST was found to be mainly dependent on the hydrophobic and hydrophilic properties of the solvents. Most of the alcohols and amines with shorter alkyl chains increased the LCST of the polymers but those with longer chains decreased the LCST. Trifluoroethanol (TFE) showed a strong LCST decreasing effect in spite of its short chain, which seems to be due to its strong hydrophobicity. Temperature-induced molecular weight fractionation of the polymer bearing MPEG350 (M _w= 350) and L-aspartic acid ethyl ester as a side group was carried out by using the LCST decreasing effect of TFE, and the fractionated samples were characterized by gel permeation chromatography (GPC) and ¹H- and ³¹P NMR spectroscopies. Thus it has been shown that a polymer may be fractionated to the higher and lower molecular weight fractions with smaller polydispersity indices (PDI): the polymer with the weight-average molecular weight (M _w) of 73,500 with PDI of 5.56 was fractionated to those of 106,000 with PDI of 4.37 and 11,000 with PDI of 1.86. Received: 8 September 2000/Revised version: 6 November 2000/Accepted: 9 November 2000     

Rheological properties of concentrated polymer solution: Polybutadiene in good and θ solvents

The zero shear viscosity, η° of three polybutadiene samples having different molecular weights over a wide range of concentration (1.0–35.0% polymer) in good and θ solvents has been studied. Superposition of viscosity data has been made to give a single composite curve for each solvent by shifting them vertically by a factor (M°/M)^3.4, where M° represents the molecular weight of the reference sample. The shift factor is found to be proportional to M^3.4 in the region of higher concentration, which indicates that the 3.4-power law is valid for the data of polybutadiene. The double-logarithmic plots of relative viscosity η°_r as a function of c⁵M^3.4 yielded a single composite curve approximating a straight line with slope of unity at the higher values of the variables. The results indicate that over a considerable range of the variables (molecular weight and concentration) at a constant temperature, the relative viscosity is a single function of c⁵M^3.4. The results for double-logarithmic plots of zero shear specific viscosity η°_csp as a function of concentration confirmed those observed in polycholoroprene samples studied earlier that the η0_sp values in θ solvents at higher concentration region are found to be higher than those found in good solvents, whereas in the moderately concentrated region the values are just opposite in θ and good solvents. The viscosity crossover in θ solvents is not as sharp as is found in case of polychloroprene samples and that crossover, too, has taken place in the range of concentration of 11.7–31.6% polymer, which is comparatively higher than that of polychloroprene samples (6.06–21.0% polymer). The results indicate some relation between viscosity crossover and polymer polarity, supporting the idea of enhanced intermolecular association in poor solvents. To correlatethe viscosity data obtained in good and poor solvents, two methods, one given by Graessley and the other given by Dreval and coworkers involving the correlating variable c[η], were considered. The plots of relative viscosity η°, versus the correlating variable c[η] in benzene (good solvent) yielded one curve, but in the case of θ solvents (dioxane and isobutyl acetate), the same plots yielded three separate curves instead of a single curve, which is rather unusual. The appropriate correction on the correlating variable for chain contraction in the concentrated region in a good solvent moved the data to a common curve, especially in lower concentration region, but at the higher concentration region a slight overestimation of data seems to have been effected. On the other hand, the plots of log η as a function of correlating variable c[η] yielded a single curve for three samples in the good solvent benzene, but in poor solvents (diozane and isobutyl acetate) the same plots yielded three separate curves for three samples instead of a single curve, the reason for which is not known at present. However, the normalization of the correlating variable c[η] with Martin constant K_M reduced all experimental data of the polymer samples to a common curve. The correlation of the viscosity data by either of the two methods seems to be possible in the case of the nonpolar flexible polymer, polybutadiene.     

Solubility properties of poly(1,1-difluoroethylene) in dipolar aprotic solvents

A screening study of the solubility of poly(1,1-difluoroethylene) (PVF₂, M?_w = 2 × 10⁵) at room temperature in a wide variety of dipolar aprotic species has facilitated the discovery of a series of new solvents (N-methyloxazolidone, cyclic-substituted ureas) and rationalization of the data in a two-dimensional solubility map involving their dipole moment, μ, and their hydrogenx-bond-accepting (HBA) power β (Taft solvatochromic parameter). This map may be used as a predictive tool for the research of new functional classes of solvents, such as N-substituted mixed amideester of phosphoric acid or N-substituted sulfurous diamides. The variations of the intrinsic viscosity of the polymer with solvent polarity may be quantitatively analyzed using a linear multiparametric correlation which emphasizes the two opposite contributions of cavitation effects (Hildebrand solubility parameter δ) and of polymer–solvent interactions (β) on the coil expansion: [η] (dL.g^?1) = 0.792 - 1.2 × 10^?3δ2(J.cm^?3) + 1.59 β. Finally, 1,3-dimethyl-2-oxo-hexahydropyrimidine (N,N′-dimethylpropylene urea) leads to the highest value of the refractive index increment (dn/dc = ?0.065 mL.g^?1 at λ = 632 nm), and thus appears as the best solvent for light-scattering measurements.     

Flow behavior of concentrated solutions of an SBS block copolymer

The non-Newtonian viscosity of concentrated solutions of a styrene-butadiene-styrene, SBS, block copolymer was measured with a novel capillary viscometer. Polymer concentrations ranged from 0.165 to 0.306 g/cc. Apparent shear rates ranged from 1 to 10⁵ sec^?1. Five different solvents were employed. All of the flow curves can be reduced to a single master curve with the same shape exhibited by monodisperse polystyrenes and the Graessley theory. The shift factor for the shear rate axis, τ₀, approximately parallels the Rouse relaxation time, τ_R, but shows a residual concentration and solvent dependence not predicted by the Rouse form. For different solvents at the same concentration, better solvents show a minimum relative zero shear viscosity, η₀/η_s, and a maximum ratio τ_R/τ₀. It is concluded that all solvent effects are not adequately incorporated into the zero shear viscosity for the purposes of constructing master plots; however, the shape of the master plot is not affected by the solvent or the polymer block structure.     

The use of biodiesel as a green polymerization solvent at elevated temperatures

BACKGROUND: Many important polymers are produced via solution polymerization. The solvent maintains a low viscosity, which provides many practical advantages related to heat transfer, mixing and material handling. Despite these advantages, commonly used solvents often present health and environmental problems. In an effort to replace these toxic solvents, a ‘green’ polymerization solvent, namely canola‐based FAME (fatty acid methyl ester or biodiesel), was used for solution polymerizations at an elevated temperature. RESULTS: Homopolymerizations of methyl methacrylate, styrene, butyl acrylate and vinyl acetate in FAME were studied at different solvent concentrations at 120 °C. Chain transfer to solvent rate constants (C_fs) were obtained for each polymer system and Arrhenius parameters for C_fs, i.e. E_a and A, were also calculated. These new solvent data were employed in a polymerization simulator to predict rate of polymerization and number‐ and weight‐average molecular weights for these commercially important systems. Model predictions showed reasonable agreement with experimental data. CONCLUSION: FAME fulfills the demands as a polymerization solvent. From an ecological perspective, FAME provides an environmentally friendly alternative to common solvents. From an industrial perspective, using FAME as a high‐boiling polymerization solvent can increase productivity by enabling polymerizations at elevated temperatures. Copyright © 2008 Society of Chemical Industry     

Comparative studies on the effects of casting solvent on physico‐chemical and gas transport properties of dense polysulfone membrane used for CO2/CH4 separation

The effects of casting solvents on the physico–chemical and transport properties of polysulfone membranes were investigated. Comparative analysis of the properties of membranes prepared from a new solvent (diethylene glycol dimethyether, DEG) and other commonly used solvents (1‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, dimethyl sulfoxide and N,N‐dimethylformamide) were performed using gas permeation, X‐ray diffraction, scanning electron microscopy, thermogravimetric, and Fourier transform infrared spectroscopy analyses. The degree of polymer–solvent interaction was evaluated using the solvent molar volume, and Hansen and Flory–Huggins parameters. Membrane prepared from DEG displayed a relatively higher permeability of 29.08 barrer and CO₂/CH₄ selectivity of 23.12 compared to membranes prepared from other solvents. This improved performance was attributed to the better interaction between the DEG solvent and polysulfone than other solvents that were considered. DEG has the highest molar volume of 142.280 cm³/mol and the lowest Flory–Huggins parameter of 0.129. Thus a thorough evaluation of polymer–solvent interaction is very crucial in preparing membranes with optimum performance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42205.     

Compatibility of polyacrylates and polymethacrylates with poly(vinyl chloride): 2. Measurement of interaction parameters

Interactions of various solvents with poly(vinyl chloride) and a series of polyacrylates and polymethacrylates have been studied by inverse gas chromatography. Values of the interaction parameters χ₁₂ have been calculated and show the importance of specific interactions between the polymers and the solvents. Low values of χ₁₂ indicating a strong interaction were found for the polyacrylates and polymethacrylates with a proton donating solvent, chloroform, and for the poly(vinyl chloride) with some proton accepting solvents, especially butan-2-one. Interactions of solvents, with mixtures of poly(vinyl chloride) with some compatible polyacrylates and polymethacrylates, have also been studied. From this, and using the values of χ₁₂ found above, values of the polymer-polymer interaction parameters χ₂₃ have been calculated. Low values of χ₂₃, indicating a strong interaction were found, especially for polymethacrylates and polyacrylates with shorter ester side chains. Lower values were obtained for polymethacrylates than polyacrylates again indicating greater interactions. These results fit in well with the results of a previous paper where we found that the polymers with longer ester side chains were not compatible with PVC or phase separated on heating, and that fewer acrylates than methacrylates are compatible with PVC.     

Lithium ion transport through nonaqueous perfluoroionomeric membranes

The transport properties of lithiated perfluorinated ionomers imbibed with nonaqueous solvents and solvent mixtures were studied. Polymeric ion‐exchange membranes have potential use in the next generation single‐ion secondary lithium polymer batteries, where the lithiated form of the membrane is used as a polymer electrolyte. The novelty of the approach for lithium battery applications lies in the advantage offered by a transference number of unity, no additional salt (e.g., LiPF₆) is needed, and the excellent physical and chemical stability of the fluoropolymers. Ion‐exchange membranes were converted to the Li⁺ salt form and analyzed for total conversion using FT‐IR. Nonaqueous solvents and solvent mixtures were imbibed into the membranes in a glove box, and the uptake was measured over time. A four‐point probe was used to determine the ionic conductivity based on impedance measurements performed over a frequency range of 10 to 35,000 Hz. Conductivities exceeding 10^?4 S/cm with transference numbers of unity were achieved making these ionomeric membranes potentially useful in rechargeable lithium polymer batteries.     

Polymer/carbon nanotube composites for liquid sensing: Selectivity against different solvents

An electrically conductive polymer composite (CPC) based on polycarbonate filled with 1.5 wt.% carbon nanotubes (CNTs) was investigated regarding its solvent selectivity when used as a sensor material for liquid detection. Based on the electrical response characteristics of the CPC when immersed in different solvents, “good” and “bad” solvents out of 59 test liquids were detected and the Hansen solubility parameters of the CPC were calculated using the “Hansen software” to be δ_D = 18.4 ± 0.2 MPa^0.5, δ_P = 10.9 ± 0.8 MPa^0.5, and δ_H = 4.1 ± 0.5 MPa^0.5.Based on the CPC's and solvents' Hansen solubility parameters the affinity between CPC and solvent represented by the distance in Hansen space was determined. As a second parameter the molar volume of the solvent molecules was used to describe the selectivity of the CPC by means of a quarter circle like area clearly separating “good” and “bad” solvents in a so-called solvent map.Whereas the Hansen solubility parameters are based on thermodynamics, the influence of the solvents' molar volume on the CPC's selectivity can be explained by diffusion processes. When increasing the molar volume of solvents having a similar chemical structure, a limiting value of the molar volume was found above which no solvent diffusion into the CPC was observed.Using this large number of solvents it could be clearly shown that the electrical response kinetics upon immersion into “good” solvents cannot be correlated with the Hansen solubility parameters of the CPC or their difference between CPC and solvent but is determined by the diffusion kinetics, which is governed by the solvents molecule size.