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Density functional theory (DFT) analysis is used to shed light on the intricate effects of the Co2C and Co/Co2C catalyst crystal facets on the selectivity of the C2 oxygenate and hydrocarbon formation in Fischer–Tropsch synthesis. Three representative low-index Co2C (101), (110), and (111) surfaces, varying in surface energy from low and medium to high, are model examples of different Co2C exposed crystal facets. Since CHx (x = 1–3), CO, and H species are the key intermediates critical to the C2 oxygenate selectivity, all Fischer–Tropsch reactions related to CHx (x = 1–3) species, including CO insertion into CHx (x = 1–3) and CHx + CHy (x, y = 1–3) coupling to form C2 species (C2Hx and C2HxO), as well as the hydrogenation and dissociation of CHx (x = 1–3) to form C1 species (CH4 and C), are used as examples examined at a typical FTS temperature of 493 K. On Co2C (101) and (110) surfaces, CH and CH2 species are dominant form of the CHx species, CH self-coupling to C2H2 and CH coupling with CH2 to CH2CH is ...

Based on the knowledge that cationic polymers with different topographical structures behave differently in gene transfection process, herein, we synthesized three biodegradable poly(amido amine)s (PAAs) with the same repeating units and molecular weights except for degree of branching: linear PAA (LPAA), low-branched PAA (LBPAA), and high-branched PAA (HBPAA). We found that LBPAA could more effectively compact pDNA into positively charged nanoparticles than both HBPAA and LPAA. LBPAA polyplexes had the highest transfection efficiency among the three PAA polyplexes, and the difference in transfection efficiency is mainly attributed to the endocytosis rate. The cytotoxicity of PAAs was negligible at the transfection doses, probably due to the degradable disulfide bonds. Therefore, we could use branching as a parameter to simply tune a polymer's cellular uptake behavior and transfection efficiency. Biotechnol. Bioeng. 2013; 110: 990–998. © 2012 Wiley Periodicals, Inc.

The low-pressure isothermal sorption of CO2 in poly(ionic liquid)s (PILs) with varied structures including different cations, anions, backbones, and substituents was investigated to probe structure effects on the CO2 sorption. An ammonium cation with short alkyl group, BF4 anion, and polystyrene backbone was found to favor CO2 sorption in PILs. CO2 sorption in the PILs fitted the dual-mode model very well, suggesting that the CO2 sorption consists of dissolution in the polymer matrix and Langmuir sorption in the microvoids.

This review presents recent advances and applications of statistical associating fluid theory (SAFT), which has been extended in the past few years, conceptually and practically, to improve its performance and to represent thermodynamic properties of complex systems, such as associating polymers, polydispersed polymers, aqueous electrolytes, dipolar and quadrupolar systems, ionic liquids, near-critical systems, interfacial phenomena, crystallizable copolymers, gas hydrates, liquid crystals, biomaterials, and oil reservoir fluids, as well as dynamic properties such as viscosity.

Based on sorption experiments up to 180 bar and 75 °C, the CO2 solubility in an ammonium-type ionic polymer, such as poly(p-vinylbenzyltrimethyl ammonium tetrafluoroborate), is found to be much higher than that in an imidazolium-type ionic polymer, such as poly(1-(p-vinylbenzyl)-3-methyl-imidazolium tetrafluoroborate), which points to a cation-type effect on the CO2 sorption in polymerized ionic liquids. These two polymers remain glassy in the temperature and pressure ranges studied in this work. The CO2 solubility increases with decreasing temperature and with increasing pressure, but it reaches a limiting value, beyond which it is insensitive to pressure.

Polymer–inorganic nanocomposite membranes present an interesting approach to improve the separation properties of polymer membranes because they possess properties of both organic and inorganic membranes such as good permeability, selectivity, mechanical strength, and thermal and chemical stability. The preparations and structures of polymer–inorganic nanocomposite membranes, their applicability to gas separation and separation mechanism are reviewed.

Brominated poly(2,6-diphenyl-1,4-phenylene oxide) (BPPOdp) is synthesized as a new membrane material for gas separation. BPPOdp forms flexible membranes with higher CO2 permeability (PCO2 = 78 Barrer) and selectivity (αCO2/N2 = 30) than poly(2,6-dimethyl-1,4-phenylene oxide) (PPOdm) membranes. BPPOdp also forms nanocomposite membranes with silica nanoparticles. The nanocomposite membranes have a greatly enhanced CO2 permeability while maintaining the CO2/N2 and CO2/CH4 selectivities of the pure BPPOdp membranes. The CO2 permeability increases as the silica content increases in the membrane. The 10-nm silica nanoparticles are more effective at increasing the CO2 permeability than the 30-nm silica nanoparticles. Mechanism studies show that the enhanced permeability results from the nanogaps between the silica nanoparticles and the polymer chains due to their incompatibility.

Polystyrene-block-polyisoprene forms micelles in supercritical and subcritical propane upon cooling and decompression. These micelles decompose upon heating and compression. At constant polymer concentration, the micellization points, both isobaric and isothermal, fall around a decreasing boundary curve in pressure−temperature coordinates. This micellization boundary curve lies above the copolymer cloud-point curve and below the free-polystyrene cloud-point curve. At the onset of micellization, a trace of free polystyrene can cause a characteristic scattering peak as it precipitates upon cooling or decompression or both.

Polyethylene glycol (PEG) is grafted onto ionic polymers poly[p-vinylbenzyltrimethylammonium tetrafluoroborate] (P[VBTMA][BF4]) and poly[2-(methylacryloyloxy)ethyl-trimethylammoniumtetrafluoroborate] (P[MATMA][BF4]). Membranes made of P[VBTMA][BF4]-g-PEG and P[MATMA][BF4]-g-PEG are found to be CO2 selective for CO2/CH4 and CO2/N2 separations, and less brittle than those made of pure P[VBTMA][BF4] and P[MATMA][BF4]. At the same permeability, the P[MATMA][BF4]-g-PEG membranes are demonstrated to have a higher CO2 selectivity than the previous polymeric membranes. The selectivity of both P[VBTMA][BF4]-g-PEG and P[MATMA][BF4]-g-PEG is primarily due to the solubility differences, not the diffusivity differences.

Atom transfer radical polymerizations (ATRPs) of 1-(4-methacryloyloxy-benzyl)thymine (MAT) and 9-(2-methacryloyloxyethyl)adenine (MAA) were conducted for the synthesis of DNA-base functionalized polymers. The association equilibrium constant Kasso between MAT and MAA and the complexation equilibrium constant Kcomp between the corresponding polymers PMAT and PMAA were determined. A zipper-like diblock copolymer, PMAT-b-PMAA, was prepared by anchoring the PMAT and PMAA blocks on the ortho-positions of a pyridine ring via a successive two-step ATRP. Dynamic light scattering and atom force microscopy confirmed that the block copolymer had a V-shaped configuration in dimethylsulfoxide/N,N-dimethylformamide. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5995–6006, 2006

Ammonium-based ionic liquid monomers and their corresponding polymers [poly(ionic liquid)s] are synthesized and characterized for CO2 sorption. The polymers have much higher CO2 sorption capacities than the room-temperature ionic liquids and imidazolium-based poly(ionic liquid)s. For example, P[VBTMA][PF6] with polystyrene backbone has a CO2 sorption capacity of 10.67 mol%. The CO2 sorption is selective over N2 and O2. The effects of cation, backbone, substituent, anion and crosslinking on CO2 sorption are discussed. The sorption mechanism study indicates that CO2 sorption by the poly(ionic liquid)s is a bulk and surface phenomenon.

In SAFT1-RPM approximations of CO2−H2O and CO2−H2O−NaCl systems, relevant to oil recovery and CO2 sequestration, CO2 is modeled as a molecule with three association sites, two sites of type O and one site of type C. H2O is modeled as a molecule with four association sites, two sites of type O and two sites of type H. The salt is modeled as a molecule composed of two charged, but nonassociating, spherical segments, of which one represents the cation and one represents the anion. For the CO2−H2O system, only one type of cross-association is assigned, i.e., between the site of type O in CO2 and the site of type H in H2O. Using temperature-dependent parameters, SAFT1-RPM is found to represent the density and equilibrium data for the CO2−H2O system, including the minimum H2O concentration in the CO2-rich phase in the y-P diagram. For the CO2−H2O−NaCl system, an additional binary interaction constant is used, the same for both CO2−Na+ and CO2−Cl- pairs, which is needed to correct the short-range interactions. S...

A series of imidazolium-based ionic liquid monomers and their corresponding polymers (poly(ionic liquid)s) were synthesized, and their CO2 sorption was studied. The poly(ionic liquid)s had enhanced CO2 sorption capacities and fast sorption/desorption rates compared with room temperature ionic liquids. The effects of the chemical structures, including the types of anion, cation, and backbone of the poly(ionic liquid)s on their CO2 sorption have been discussed. In contrast to room temperature ionic liquids, the polymer with PF anions had the highest CO2-sorption capacity, while those with BF or Tf2N− anions had the same capacities. The CO2 sorption and desorption of the polymers were fast and reversible, and the sorption was selective over H2, N2, and O2. The measured Henry's constants of P[VBBI][BF4] and P[MABI][BF4] were 26.0 bar and 37.7 bar, which were lower than those of similar room temperature ionic liquids. The preliminary study of the mechanism indicated that the CO2 sorption of the polymer particles was more absorption (the bulk) but less adsorption (the surface). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5477–5489, 2005

Cloud-point pressures are measured and correlated with the SAFT1 equation of state for polystyrene/propane and poly(4-methyl styrene)/propane. The SAFT1 parameters for polystyrene are then used to correlate polystyrene solutions in other solvents, for example, n-butane and n-pentane.

The SAFT1 equation of state captures the melting retrograde behavior for a ternary system of poly(ethylene-co-octene-1) + isooctane + ethylene. The melting temperature minimum depends on the polymer branch density, solvent composition, polymer concentration, and polymer molecular weight, in decreasing order of sensitivity. Furthermore, the effects of the solvent/antisolvent ratio and polymer concentration on the melting temperature are nonmonotonic, that is, their sign may change in going from low to high pressures. Finally, the sign of the slope of the melting curve depends only on the difference between the partial molar volume of polymer in solution and the molar volume of pure solid polymer.

A model of copolymer solids hypothesizing inclusion of the comonomer units in the crystalline domain is applied to calculation of solid−liquid transitions. Such an inclusion model is compared to an exclusion model hypothesizing exclusion of the comonomer units from the crystalline domain. Both models are used with the copolymer SAFT equation of state1 to represent the solid−liquid transition temperatures of polyethylene and poly(ethylene-co-octene-1) in propane, isooctane, and a mixture of isooctane + ethylene. The inclusion model is found to be more predictive and to have a correct high polymer-concentration limit, which is the melting temperature of pure polymer. Furthermore, the inclusion parameters, the fold energy and the energy penalty, are found to be solvent- and composition-independent, while the exclusion parameter, the crystallizability, is found to be both solvent- and composition-dependent.

The SAFT1 equation of state is extended using Wertheim's theory to model associating fluids and tested on pure alkanols and mixtures containing alkanols. For small 1-alkanols, SAFT1 is found to represent the vapor pressure and liquid density. The SAFT1 parameters are shown to be well-behaved and hence possible to estimate for high-molecular-weight 1-alkanols and hydroxy polymers on the basis of their molecular weight alone.

Fluid−liquid pressures are measured and correlated with two SAFT equations of state for poly(ethylene-co-octene-1) solutions in supercritical ethylene at temperatures up to 180 °C. These cloud-point pressures are found to depend strongly on the molecular weight of the polymer and the branch density but weakly on the polymer concentration in the range from 0.05 to 0.15 polymer weight fraction. EO solutions in ethylene are found to exhibit U-LCST behavior.

The cloud-point pressures and critical polymer concentration are measured for poly(ethylene-co-hexene-1)+propane solutions up to 180°C and 500 bar using a light-scattering probe. The measured cloud-point data agree with those calculated from SAFT1.

Fluid−liquid (FL) and fluid−solid (FS) phase transitions are measured and correlated with two SAFT equations of state for poly(ethylene-co-octene-1) solutions in sub- and supercritical propane. The polymer concentration is found to have a weak effect on both FL and FS transitions in the range of this study (0.01−0.1 polymer weight fraction). Increasing molecular weight is found to increase the FL pressure and FS temperature, whereas increasing branch density is found to decrease the FL pressure and FS temperature.

Isotactic polypropylene (iPP) and ethylene-butene (EB) copolymers were dissolved in supercritical propane and precipitated by rapid expansion of supercritical solution (RESS) and isobaric crystallization from SS (ICSS). The cloud-point pressures of the ternary solutions were found to increase as the immiscibility of PP and EB copolymer increased (i.e., as the number of ethyl branches in the EB copolymers decreased). The RESS process resulted in microfibers and a trace of microparticles, and the EB copolymer domains in the blends decreased in size as the ethyl branch content in the EB copolymers increased. The thermal stability of the copolymer domains was improved by synthesizing thermoplastic vulcanizate (TPV) from PP and ethylene-propylene-diene terpolymer in a supercritical propane solution followed by RESS. The ICSS process produced microcellular polymeric foamlike materials, but the two polymers were precipitated independently by thermally induced phase separation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1478–1487, 2000

A solid–liquid equilibrium (SLE) model is developed on the basis of an equation of state referred to as copolymer SAFT. This SLE model is demonstrated for hydrocarbon solutions containing totally and partially crystallizable solutes. Initially regressed and tested on the solubility data for naphthalene, normal-alkane, and polyethylene, this model is used in a sensitivity study to understand the effects of crystallizability, melting temperature, molecular weight, and pressure on solid–liquid and liquid–liquid transitions of polyethylene in subcritical and supercritical propane.

The square-well fluid thermodynamics and liquid structure derived from Barker−Henderson's perturbation theory, including a truncation correction, are used within a SAFT framework to develop a prototype of an engineering equation of state for alkane chains, referred to as SAFT1. For small n-alkanes, not only the vapor pressure and liquid density, but also the second virial coefficient, heat of vaporization, and heat capacity, are found to be more accurate. SAFT1 parameters are well behaved and hence easy to estimate reliably for high-molecular-weight alkanes and polyolefins. These parameters are found to predict cloud points in mixtures of homo- and heterosegmented molecules, such as polyolefins, without fitting.

New thermoplastic vulcanizates (TPV's) have been synthesized from isotactic polypropylene and ethylene−propylene−diene terpolymer (EPDM) in a supercritical propane solution. The ternary solution of polypropylene and EPDM in supercritical propane exhibited less solubility than the corresponding binary solutions of polypropylene or EPDM separately in propane. Higher pressure in the supercritical polymer solution enhanced the mutual solubility of the two polymers. EPDM was cross-linked with tert-butyl peroxide while in supercritical solution. On lowering the pressure while remaining above the melting temperature of the polymers, the supercritical TPV gel phase separated in a manner consistent with spinodal decomposition. On isobaric cooling of the supercritical TPV gel, the polypropylene crystallized, freezing the morphology. The cross-linking of EPDM in the homogeneous supercritical propane solutions was found to be nearly complete. The final TPV's were phase separated, exhibiting two melting transitions. T...

The copolymer SAFT equation of state is found to represent phase transitions in the normal-alkane and methyl-alkane solutions in methane, ethane, propane, and n-hexane, the polyethylene and poly(ethylene-co-olefin-1) solutions in propane, and the polystyrene solutions in n-butane. The pure-solute parameters are all estimated on the basis of the molecular weight and structure only, and the one temperature-independent and system-independent (within each class of solutes) binary parameter is set equal to a constant. The segment energy of the methyl branches is found to be around 160 K, which is lower than the corresponding backbone energy, while the segment energy of the benzene branches is found to be around 222 K for polystyrene, which is higher than the corresponding backbone energy. The alkyl branches are found to promote the polymer miscibility while the benzene branches are found to inhibit the polymer miscibility in propane.

A prototype equation of state, developed on the basis of thermodynamic perturbation theory of the first order (TPT1), using the Lennard-Jones potential for the reference fluid, is found to represent pure-fluid and binary phase equilibria in the systems of small chain molecules, such as normal alkanes.

Cloud-point and coexistence pressures, sub- and supercritical, are determined experimentally for a series of ethylene and propylene solutions of nearly monodisperse and polydisperse poly(ethylene-co-propylene), referred to as PEP. The cloud-point and coexistence pressures are found to be close for solutions of nearly monodisperse PEP polymers but not for solutions of polydisperse PEP. The SAFT parameters derived from the experimental cloud points for nearly monodisperse solutes alone are found to predict the cloud-point pressures and solubilities for polydisperse PEP as well.

Cloud-point pressures were measured for binary sub- and supercritical fluid solutions of saturated or unsaturated polyisoprene (UPEP) in ethane, ethylene, propane, propylene, and dimethyl ether up to 150°C and 1,400 bar. The polyisoprene was hydrogenated to obtain two samples of different degrees of saturation (56% and 73%). These polymers and solvents were chosen to evaluate π-π interactions between polymer/polymer or polymer/solvent molecules. π-π interactions between polymer and solvent are found to shift the cloud-point pressures in an analogous way to those found for cross-associating polymers. Preliminary correlations using the statistical associating fluid theory (SAFT) are also included.

Of the large number of equations of state available in the literature, few treat small molecules as well as polymers, association, and copolymers. Three equations of state that rigorously account for all of these effects and have been applied to real polymer systems are the lattice-fluid theory (LF), the statistical associating fluid theory (SAFT), and the perturbed hard-sphere chain theory (PHSC). We illustrate the versatility of one of these equations of state (SAFT) for modelling the phase behavior of polyolefin systems, and the effects due to molecular dissimilarity, compressibility, association, and copolymer composition.

Thermodynamic perturbation theory of the first order (TPT1) is extended to heterobonded chains, such as heteronuclear and branched copolymers. The TPT1 formalism provides the basis for a copolymer equation of state. This new copolymer equation of state, referred to as Copolymer SAFT (Statistical Associating Fluid Theory), explicitly accounts for the effects of chain heterogeneity and microstructure. In order to illustrate potential future applications, Copolymer SAFT is used to calculate high-pressure cloud points in real polymer solutions of supercritical propane + poly(ethylene-co-butene).

The effects of compressed carbon dioxide at slightly subcritical temperatures on solutions of a chloro-substituted, para-linked aromatic polyamide (PPTA-Cl) in dimethylacetamide were investigated by depolarized light spectroscopy. Pressurization of isotropic solutions resulted in polymer precipitation at a sharply defined pressure. Pressurization of nematic solutions resulted in an increase in the intensity of scattered light with no evidence of precipitation. A plausible interpretation of this observation is the occurrence of liquid−liquid phase separation into polymer-rich (anisotropic) and polymer-lean (isotropic) phases induced by the compressed carbon dioxide. The results suggest that compressed, near-critical antisolvents can be used to control the degree of anisotropy in liquid-crystalline polymeric systems.

This is a review of the phase equilibria in supercritical monomer solutions of ethylene homopolymers and copolymers, such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), poly(ethylene-co-methacrylate) (EMA), poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-methacrylic acid) (EMAA), and poly(ethylene-co-acrylic acid) (EAA). The knowledge of such phase equilibria underlies the high-pressure polyethylene (HPPE) technology. The ability to estimate such phase equilibria allows for smooth and robust process optimization during grade transitions. This is important because the HPPE technology makes it possible to minimize the product cross-contamination and, hence, to make higher-value, fluctuating-demand speciality polymers. Experimental data, phase diagrams, and patterns of phase disengagement presented in this paper are related to the reactor system, the high-pressure separator (HPS), and the high-pressure recycle system. These data and diagrams are used to characterize the monomer-polymer miscibility defined as a cloud point transition. The cloud point pressures in such systems are found to depend on thermodynamic parameters, such as temperature and composition, and on the dissimilarity between the polymer and the monomer. This dissimilarity is characterized in terms of the differences in molecular weight and density (e.g., for LDPE and LLDPE), in polarity (e.g., for EVA and EMA), and in association (e.g., for EAA and EMAA)

Polystyrene is characterized as a mixture of a finite number of discrete pseudocomponents. Solubilities and partition coefficients of the pseudocomponents in propane and in ethane are measured in semibatch experiments at temperatures ranging from 323 to 453 K and pressures up to 67 MPa. An equation of state based on the statistical associating fluid theory (SAFT) is used to correlate the data. Increasing temperature and pressure are found to increase the solubilities and partition coefficients, but decrease selectivities. The solubility of pseudocomponents is also found to depend on the molecular weight distribution of the polymer

A robust but rigorous flash algorithm allows for simulating multicomponent two-phase equilibria in supercritical asymmetric solutions that contain very large and very small components, such as polymers and supercritical solvents or monomers. The approach is to solve simultaneously all the equilibrium and material balance equations using a Newton iterative procedure in the framework of block algebra. The SAFT equation of state is used to estimate the required thermodynamic properties. This approach is illustrated with an example of single-stage fractionation of polyethylene with supercritical ethylene and 1-hethylene. The calculated solvent capacities and selectivities are related to ethylene concentration, pressure, and temperature

Polycrystalline spherulites and microfibrils are obtained from a substituted para-linked polyamide [COPh(Ph)CONHPh(Me)Ph(Me)NH] n in a supercritical antisolvent (SAS) process. CO 2 is contacted with 0.03-O.12 wt % polymer in DMSO and in DMF solutions in both batch and continuous modes of operation. Slow expansion of the solution produces polycrystalline spherulites in the 1-10-μm-diameter range, and the degree of crystallinity is affected by turbulence caused by CO 2 injection. A microfibrillar structure is obtained by spraying the polymer solution through a small orifice into cocurrently flowing supercritical CO 2

Binary phase equilibria of C[sub 20] +, C[sub 30] +, and C[sub 40] + ethylene are correlated with three equations of state, the Redlich-Kwong-Soave (Soave), the generalized van der Waals-Prigogine (vdW-P), and the statistical associating fluid theory (SAFT), with special emphasis on the mixture critical region. The SAFT correlation is found to be the most reliable. SAFT predictive powers are tested on C[sub 26] + ethylene and a new set of experimental data taken in this work for C[sub 36] + 1-butene and C[sub 36] + ethylene + 1-butene. The SAFT predictions are found to be in good agreement with the experimental data. Equally important, the SAFT predictions allow for understanding the continuous transition of phase behavior, from type A (C[sub 36] + 1-butene) through LCST (C[sub 36] + ethylene + 1-butene) to U-LCST (C[sub 36] + ethylene).

Vapor-liquid equilibria for a binary system of carbon dioxide and 1-methylnaphthalene are measured in the range of 50 to 250° and 40 to 160 bar, in a flow apparatus. The experimental data are correlated with three equations of state, the Statistical Associating Fluid Theory (SAFT), the Perturbed Hard Chain (PHC), and the Soave (Soave). The calculated mutual solubilities and distribution coefficients (K-factors) are found to be in reasonable agreement with the experimental data.

A new 2-kbar optical cell is developed for cloud-point measurements on polymer films. Pressure dependence of melting points and crystallization temperatures for poly(ethylene oxide) (PEO), measured in this cell, is found to be linear up to 200 MPa (2000 bar). Slopes (dT m /dP) of 0.111, 0.126, and 0.126°C/MPa are obtained independently from optically measured cloud points, from P-V-T data, and from estimates based on the Clapeyron equation using DSC data, respectively. The approximation of the Clapeyron equation used, which requires only the apparent ambient-pressure properties of a semicrystalline polymer, is shown to be consistent with the high-pressure experimental data

Phase boundaries for a series of poly(ethylene-propylene) copolymers having uniform structure but differing in molecular weight, from 800 to nearly 100,000, in various solvents are determined experimentally up to 200°C and 600 bar. Propylene, 1-butene, and 1-hexene are used as solvents. A free-volume sensitive LCST is found near the solvent critical point and an energy sensitive UCST is found away from the solvent critical point. The effect of supercritical ethylene on the phase behavior of these systems is investigated. Statistical Associating Fluid Theory (SAFT) is used to model the phase behavior of these systems. SAFT was chosen because the parameters for the polymers can be calculated from generalized correlations based on the polymer molecular weight. SAFT is able to correlate the experimental data accurately using only one binary interaction parameter that is polymer molecular weight dependent. In addition, calculations are shown using the polymer solution theory of Flory and Patterson.

Temperature-pressure and pressure-concentration cloud-point transitions were measured for solutions of ethylene-propylene copolymer (PEP) in ethylene and in propylene in the critical region. The cloud points were visually observed in variable-volume optical cells up to 200°C and 2000 bar. While UCST, LCST, and U-LCST transitions were observed for PEP solutions in propylene, only U-LCST behavior was observed for PEP solutions in ethylene for the molecular weight range investigated (790–96000 g mol ). Statistical Associated Fluid Theory (SAFT) was used to correlate the experimental cloud points.

Statistical associating fluid theory (SAFT) is used to calculate solubilities of solid polynuclear aromatic hydrocarbons (PNA's), such as naphthalene, phenanthrene, pyrene, and anthracene, in supercritical ethylene and supercritical ethane. Good agreement with experimental data is obtained at temperatures from 12 to 75°C and at pressures up to 550 bar. Only one binary adjustable parameter is needed, which has a simple linear temperature dependence. The SAFT model is applied to predicting selectivities and capacities of supercritical ethane and ethylene for separating PNA's by size and structure

The deuterated homopolymers and their corresponding polystyrene-block-polybutadiene and polystyrene-block-polyisoprene copolymers require lower cloud pressures than their hydrogenous analogues to dissolve in a compressible alkane solvent, such as propane. For symmetric diblocks, deuteration reduces the micellization pressure. By contrast, for asymmetric diblocks with a long diene block relative to the styrene block, deuteration can increase the micellization pressure. All in all, however, the deuteration effects, while measurable, do not qualitatively change the principal diblock properties in compressible propane solutions, such as pressure-induced micelle decomposition, micelle formation and micelle size, and their temperature dependence. Therefore, isotope labeling should be a useful approach to neutron-scattering characterization for styrene-diene block copolymers in compressible alkane systems.

Statistical Associating Fluid Theory (SAFT) has been extended to many real, molecular, and macromolecular fluids, such as chain, aromatic, and chlorinated hydrocarbons, ethers, alkanols (aliphatic alcohols), carboxylic acids, esters, ketones, amines, and polymers, having molar mass up to 100000. The key result of this work is an accurate and physically sound equation of state for predicting density, vapor pressure, and other fluid properties

Atom transfer radical polymerization (ATRP) generally requires a catalyst/initiator molar ratio of 0.1 to 1 and catalyst/monomer molar ratio of 0.001 to 0.01 (i.e., catalyst concentration: 1000-10,000 ppm versus monomer). Herein, we report a new copper-based complex CuBr/N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) as a versatile and highly active catalyst for acrylic, methacrylic, and styrenic monomers. The catalyst mediated ATRP at a catalyst/initiator molar ratio of 0.005 and produced polymers with well-controlled molecular weights and low polydispersities. ATRP occurred even at a catalyst/initiator molar ratio as low as 0.001 with copper concentration in the produced polymers as low as 6-8 ppm (catalyst/monomer molar ratio = 10(-5)). The catalyst structures were studied by X-ray diffraction and NMR spectroscopy. The activator CuIBr/TPEN existed in solution as binuclear and mononuclear complexes in equilibrium but as a binuclear complex in its single crystals. The deactivator CuIIBr2/TPEN complex was mononuclear. High stability and appropriate KATRP (ATRP equilibrium constant) were found crucial for the catalyst working under high dilution or in coordinating solvents/monomers. This provides guidance for further design of highly active ATRP catalysts.

"Stealth" nanoparticles made from polymer micelles have been widely explored as drug carriers for targeted drug delivery. High stability (i.e., low critical micelle concentration (CMC)) is required for their intravenous applications. Herein, we present a "core-surface cross-linking" concept to greatly enhance nanoparticle's stability: amphiphilic brush copolymers form core-surface cross-linked micelles (nanoparticles) (SCNs). The amphiphilic brush copolymers consisted of hydrophobic poly(epsilon-caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) or poly(2-(N,N-dimethylamino)ethyl methacrylate) (PDMA) chains were synthesized by macromonomer copolymerization method and used to demonstrate this concept. The resulting SCNs were about 100 times more stable than micelles from corresponding amphiphilic block copolymers. The size and surface properties of the SCNs could be easily tailored by the copolymer's compositions.

Polymer solutions in supercritical fluids are unique because their phase behavior can be easily tuned with density. The statistical associating fluid theory (SAFT) captures the relationship between the molecular forces and the bulk phase behavior in such systems. Quantitative phase diagrams and partition coefficients can be generated with SAFT on the basis of molecular structure and size. Such data are key to understanding the selectivity of supercritical fluids, and the role of staging in macromolecular phase separations.

Experimental and calculated phase equilibria are reported for two systems containing propane and petroleum-derived oil mixtures near 400 K and pressures to 55 bar; these conditions are close to critical. In the first system, the oil is rich in saturated hydrocarbons; in the second system, the oil is rich in aromatic hydrocarbons. For both oils, number-average molecular weights are in the range 300-350. Solubilities in two equilibrium phases, measured with a flow-cell apparatus, are correlated with the perturbed-hard-chain equation of state wherein the composition of the heavy hydrocarbon is described by a continuous distribution function. A simple procedure is proposed to derive a molecular-weight distribution from boiling-point data.

Statistical associating fluid theory coupled with the restricted primitive model (SAFT1-RPM), previously proposed for representing single-salt solutions in water, is extended to multiple-salt solutions using a mixing rule for the hydrated diameter. A binary adjustable parameter in this mixing rule, for a pair of salts, is obtained from experimental osmotic coefficients of the corresponding ternary system. The ternary systems considered contain water and all pairs of NaCl, KCl, NaBr, and KBr. LiCl + NaCl and LiCl + KCl pairs are also correlated. The adjustable parameters are used to predict the density of the ternary systems with or without common ions, the solubility of two ternary systems, and the osmotic coefficient of a quaternary NaCl−KCl−LiCl−H2O solution.