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What should people do with the huge amount of CO2 captured? CO2 to CO is a promising way for using carbon resources because CO is one component of syngas for the production of many important synthesis intermediates such as dimethyl oxalate (DMO). Hydrogenation of DMO provides an economical and eco-friendly approach for the synthesis of methyl glycolate, ethylene glycol (EG), and ethanol, which is often determined by the reaction conditions and catalysts with different active sites. Thus, DMO or EG is also an important carbon carrier or CO2 utilization product. Also, DMO hydrogenation is a representative reaction for studying the structure–activity relationship in C═O/C–O bond hydrogenation. Therefore, this work provides a comprehensive review of the progress in DMO hydrogenation from the perspective of constructing and stabilizing the active sites. The silver and copper based catalysts with different structures and morphologies used for DMO hydrogenation have been discussed with regard to their catalytic performance and reaction mechanism. The synergy of Cu0 and Cu+ in DMO hydrogenation has been questioned, and new active sites are proposed with more experimental evidence. New reaction routes, hybrid active sites, and the effect of catalyst structure on the active sites for DMO hydrogenation have been achieved and reviewed. Moreover, a strategy of introducing organic additives to improve EG yield and stabilize copper species has been described. This work may help advance the understanding of active sites in DMO hydrogenation and guide the future rational design and fabrication of highly stable and low-cost DMO hydrogenation catalysts.

CO2−CH4 reforming into syngas is an effective approach to the utilization of these two greenhouse gases. In this study, nano-structured Ni-based catalysts supported on spinel (MgAl2O4) for CO2−CH4 reforming were synthesized and evaluated under 750–900 °C, it performed with extremely high catalytic reactivity that the conversions of CO2 and CH4 were 90% and 97% at 900 °C, with gas hourly space velocity (GHSV) as high as 912,000 ml gCat−1 h−1, which is 76 times higher than the GHSV reported in other literatures. Also, the nano-structured Ni based catalysts showed excellent durability with nearly zero deactivation in 10 h. Interestingly, the Ni-based catalysts did not need initial H2 reduction as required with state-of-the-art reforming catalyst. The fresh Ni-based catalysts mainly consist of NiO and MgAl2O4 crystallites, while the spent ones mostly contain Ni0 (about 10 nm) and MgAl2O4 crystallite.

In this paper, using carbonized hazelnut shells as the raw material and sodium amide as both activator and nitridation agent, N-enriched carbonaceous sorbents were successfully made by an one-step ...

With great effort, the Paris Agreement set goals designed to address climate change, but far more effort will be necessary to meet those goals due to the lack of transformational CO2 capture technologies that are cost-effective. This research is designed to overcome the shortcomings of conventional CO2 capture technologies (i.e. the cost, health impacts, and environmental impacts of amines) by using a titanium oxyhydroxide (TiO(OH)2) catalyst and a potassium carbonate/bicarbonate sorbent (K2CO3/KHCO3, respectively). Nanostructured TiO(OH)2 as a catalyst is able to accelerate desorption processes; the acceleration of CO2 desorption is of greater significance because the process consumes more energy than the sorption process. Experimental results show that the use of nanostructured TiO(OH)2 increases the amounts of desorbed CO2 by as much as 1200%, if not higher. Cyclic sorption-desorption testing combined with material characterization shows that both catalyst and sorbent are stable even after 50 cycles. One major benefit of the kinetic enhancement from this catalyst/sorbent system is the reduction of temperature needed to desorb CO2; waste heat may be sufficient to provide all or most of the energy required for CO2 capture. Thus, the energy cost of CO2 capture will be significantly reduced, which may keep electricity prices low, avoiding a decrease in the global economy in order to avert global climate change impacts. Another significant benefit of this system is that this inorganic system is environmentally safe, clean, and non-carcinogenic.

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 ...

The objective of this research is to investigate the effect of steam on reducing carbon deposition during CH4 chemical looping combustion (CLC) on a fixed bed reactor. Steam proved to be significantly effective not only for the fuel utilization efficiency of CLC but also for the stability of the oxygen carrier (OC). The evaluation tests were performed with CuO/γ-Al2O3 OCs prepared with three different methods. The results showed that OC prepared using co-precipitation method performed the best with the highest reactivity for CH4 combustion at low temperature (700 °C) compared to that prepared using mechanical mixture and impregnation methods. It was also found that the carbon deposition was the main reason for the low combustion efficiency and the deactivation of OCs in redox cycles. For OCs at 800 °C, after 10 cycles without steam, 25–44% CO2 selectivity reductions were observed, accompanied by Barrett-Joyner-Halenda (BJH) pore volume decreases of 31–47%. With the steam introduction, the CO2 selectivity consistently achieved ∼100% in 10-cycle CLC, and the pore volumes of OCs decreased by only 11–22%, which was mostly attributed to the carbon-steam gasification reaction. The OCs for CH4 CLC with and without steam were characterized by using different methods, including surface area and pore analysis, thermal gravimetric analysis (TGA), X-ray diffraction (XRD), H2 temperature programming reduction (TPR), and scanning electron microscope (SEM). The results demonstrated that steam could easily gasify the carbon deposition, greatly intensify the redox degree of OCs at 800 °C, and strengthen the redistribution of Cu on the surface of Al2O3, contributing to the fine and uniform distribution of CuO. Therefore, steam can be successfully used for considerable enhancement of the overall performance of CH4 CLC.

Carbon nanofibers (CNFs) have wide applications in various high-tech areas. The demand for CNFs can exponentially increase due to the rapid development of advanced functional materials. Accordingly, a transformational progress is being made in synthesizing CNFs, especially functionalized CNFs. A dominant CNF synthesis pathway is catalytic chemical vapor deposition (CCVD). Therefore, the goal of this work is to review the most recent progress in CCVD synthesis of functional CNFs and to understand how the process conditions and catalysts, especially metal catalysts, affect the physical and chemical properties of the produced CNFs.

Rare earth elements (REEs) are in high demand as critical materials in modern green and other advanced technologies. This review focuses on the recovery of REEs from waste with ionic liquids (ILs) as green dilutants and extractants to tackle the REE supply challenge. Extraction mechanisms in different extraction systems, including pure ILs, non-functional ILs with extractants, and functional ILs, are discussed in depth. The IL-based extraction process is different from the traditional molecular solvent-based extraction process. In addition, stripping is crucial to recovering ILs, and supercritical CO2 (Sc-CO2) is introduced to recover REE complexes from the IL phase. Also, Sc-CO2 can accelerate the whole extraction process by enhancing mass transfer. The challenge is to understand the extraction mechanism of the IL/Sc-CO2 system to advance the green recovery of REEs from waste.

Guanidine was introduced to low molecular weight linear polyethyleneimine (LPEI) via amide groups, to explore the effect of both guanidine degree and pendant chain length on its transfection behavior. The resulting guanidinoamidized LPEIs (GLPEIs) could dramatically reduce LPEI’s toxicity, enhance its DNA-packaging capability, cellular uptake and therefore transfection efficiency. These polyplexes were taken up very efficiently via caveolae-mediated endocytosis and their transfection efficiencies in ovarian cancer cells were significantly improved compared to native LPEI10k polyplexes. Among these GLPEIs, LPEI-C3-G100 showed higher DNA affinity even than LPEI25k and the highest transfection efficiency, probably due to the optimization of polymer chain flexibility. Of notice, LPEI-C3-G100 polyplexes could more effectively accumulate into cytoplasm than LPEI25k, although the transfection efficiency of LPEI-C3-G100 polyplexes was not superior to that of LPEI25k polyplexes, which would be probably attributed to the more efficient release of LPEI25k polyplexes than LPEI-C3-G100 polyplexes in the cytoplasm.

Implementing Paris Climate Accord is inhibited by the high energy consumption of the state-of-the-art CO2 capture technologies due to the notoriously slow kinetics in CO2 desorption step of CO2 capture. To address the challenge, here we report that nanostructured TiO(OH)2 as a catalyst is capable of drastically increasing the rates of CO2 desorption from spent monoethanolamine (MEA) by over 4500%. This discovery makes CO2 capture successful at much lower temperatures, which not only dramatically reduces energy consumption but also amine losses and prevents emission of carcinogenic amine-decomposition byproducts. The catalytic effect of TiO(OH)2 is observed with Raman characterization. The stabilities of the catalyst and MEA are confirmed with 50 cyclic CO2 sorption and sorption. A possible mechanism is proposed for the TiO(OH)2-catalyzed CO2 capture. TiO(OH)2 could be a key to the future success of Paris Climat e Accord., The notoriously slow kinetics in CO2 desorption hinders the development of efficient CO2 capture technologies. Here, the authors discover that nanostructured TiO(OH)2 as a catalyst is capable of dramatically increasing the rates of CO2 desorption from spent monoethanolamine.

Many sorbents have been studied for their CO2 sorption capacities with CO2 and N2 mixture. In reality, flue gases contain SO2. This research was designed to develop and evaluates an inexpensive and robust CO2 sorbent for actual flue gas. Ca(OH)2, CaO and CaCO3 were explored to serve as additives of K2CO3/γ-Al2O3 for CO2 capture. The three additives were characterized using different methods including thermal gravimetric, X-ray diffraction analyses and so on. It was found that Ca(OH)2 is the best additive of K2CO3/γ-Al2O3 for CO2 capture. The performances of K2CO3/Ca(OH)2/γ-Al2O3 were evaluated with a fluidized bed reactor under different conditions including the presence of SO2. Experimental results show that introduction of Ca(OH)2 made K2CO3/Ca(OH)2/γ-Al2O3 not only more capable in adsorbing CO2 but also more robust within SO2-containing flue gas. Thus the research work provides useful information for further development and subsequent commercialization of K2CO3/Ca(OH)2/γ-Al2O3 in coal-fired power plants.

The group of 36 warm-blooded half-bred horses (18 stallions and 18 mares) and their riders (20 men and 16 women), who ended three-day-events, were selected for the study. The horses were aged 4 to 6 years, while the riders were 19 to 34-year-old. The saliva samples were collected after each phase of the competitions. The cortisol concentration was determined using an immunoassay method. The following factors were considered: type of competition, horse sex, and rider gender. In horses, the statistically important correlation was found between the results obtained for the dressage and cross-country, for the cross-country and show jumping, and for the dressage and show jumping. An analogous comparison for the riders suggests a statistically significant correlation between the data obtained for the cross-country and show jumping. Comparing the data of horses and their riders, a significant correlation coefficient was found for the cross-country group of woman and the dressage group of men. In conclusion, the salivary cortisol level in individual horses in each phase of three-day-event was found to be repetitive. Therefore, the salivary cortisol test is demonstrated to be a useful method to evaluate the horse response to each type of competition during three-day-events.

Cancer drug delivery achieving high therapeutic efficacy and low side effects requires a nanocarrier to tightly retain the drug, efficiently reach the tumor, then quickly enter the tumor cells and release the drug. Furthermore, the nanocarrier intended for clinical applications should use materials safe as pharmaceutical excipients and its formulation (nanomedicine) should have good manufacture processes with scale-up ability. Thus, the challenge is to design safe, approvable, and easily scaled-up nanocarriers that simultaneously meet the two pairs of requirements of 'drug retention in circulation versus intracellular release' and 'stealthy in circulation versus sticky (cell-binding) in tumor' at the right places in order to deliver a cytosolic drug dose lethal to cancer cells with minimized side effects. Herein, we briefly review these elements aimed at promoting developments of translational nanocarriers.

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.

Near-critical micellization (NCM), allowing for precise pressure-tuned control of sequential block collapse and micelle formation, can be synchronized with cancer-drug encapsulation with virtually no drug losses. NCM is demonstrated to produce benign, stable nanoparticles made of PEG-b-PLLA-b-PCL triblock copolymers that are not only solvent-free and paclitaxel-rich, which reduces the body exposure to the excipients, but also nearly burst-release-free, which reduces if not eliminates its toxic side effects while enhancing its therapeutic efficacy.

A carbon filter that selectively captures CO2 from flue gas on porous carbonaceous sorbents is demonstrated in field tests. A new sorbent regeneration process, referred to as steam-aided vacuum swing adsorption (SA-VSA), uses steam under vacuum to displace CO2 from the carbon. Steam aids vacuum by reducing the partial pressure of CO2 without the need to reduce the total pressure to deep vacuum, which is a challenge for vacuum swing adsorption (VSA). In turn, vacuum prevents the bulk condensation of steam on the sorbent, which is a challenge for CO2 recovery using direct steam. Over 100 sorption–desorption cycles on flue gas produced in the lab and at two coal-fired power plants demonstrate that the SA-VSA-equipped carbon filter process can produce a nearly pure CO2 product (at least 98%) while achieving high recovery (at least 98%). While stable, flexible, and robust in achieving the very high recovery and purity targets, this technology offers ample room for improvement through process optimization and, ...

A low-pressure carbon filter process can capture carbon dioxide from combustion flue gas. This filter is filled with a carbonaceous sorbent, such as activated carbon, which has a high chemical affinity to and hence high capacity to retain CO2 but not nitrogen. This in turn leads to a high CO2/N2 selectivity, especially at low pressures. While CO2 sorption is spontaneous and rapid, its recovery from the sorbent is a challenge that determines the process efficiency. Among the desorption methods considered in this work, direct steam can produce nearly pure CO2, but it results in condensed water in the bed that reduces the sorbent capacity and requires sorbent cooling, which is slow. Vacuum desorption in the absence of water also works, but it requires low pressures, much lower than 30 Torr, to achieve substantial CO2 yields. However, a hybrid approach, referred to as “steam-aided vacuum swing adsorption” (SA-VSA), proposed in this work, is found to alleviate or eliminate these problems. Water vapor serves as...

Porous carbons synthesized by KOH activation of petroleum coke can have high surface areas, over 3000 m(2)/g, and high CO(2) sorption capacity, over 15 wt % at 1 bar. This makes them attractive sorbents for carbon capture from combustion flue gas. Quenched solid density functional theory (QSDFT) analysis of high-resolution nitrogen-sorption data for such materials leads to the conclusion that it is the pores smaller than 1 nm in diameter that fill with high-density CO(2) at atmospheric pressure. Upon increasing pressure, larger and larger pores are filled, up to about 4 nm at 10 bar. An ideal CO(2)/N(2) selectivity of such carbon materials tends to decrease substantially upon increasing pressure, for example, from about 8-10 at 1 bar to about 4-5 at 10 bar. All in all, this work confirms the robust CO(2)-filling properties of porous carbon sorbents, their low-pressure selectivity advantages, and points to the critical role of1 nm pores that can be controlled with activation conditions.

Pressure-tuned propane capacity and selectivity for polystyrene-block-polybutadiene allows for random molecular solutions at high pressures, micellar solutions at moderate pressures, and bulk phase...

Paclitaxel, an expensive first-line anticancer drug, is known to have better pharmacokinetics and therapeutic efficacy if encapsulated in polymeric micelles. However, the conventional encapsulation methods using incompressible aqueous solutions are limited to low drug loading, less than 3% of micelle weight, and low efficiency, more than two-thirds of the drug in solution remains unencapsulated, and hence wasted, not to mention the burst release problems. This work demonstrates that expansion of near-critical fluid solutions, for example in compressible dimethyl ether and trifluoromethane not too far from their critical region, can lead to a much higher drug loading, for example in micelles formed from poly(ethylene glycol)-block-poly(e-caprolactone) (PEG-b-PCL). By controlling the drug precipitation within the micellar solution region, the loading of paclitaxel in PEG-b-PCL can reach over 12% with a loading efficiency of 87%, which is unattainable by conventional methods. Moreover, the burst release frac...

In contrast to incompressible liquid solutions, compressible near-critical solutions of block copolymers allow for controlling rapid structure transformations with pressure alone. For example, when dissolved in near-critical propane, polystyrene-block-polybutadiene can form a random molecular solution at high pressures, a micellar solution at moderate pressures, and a solvent-free precipitate at low pressures. In contrast to the unstructured virgin copolymer, such a propane-treated precipitate rapidly self assembles toward structures characteristic of equilibrated block copolymers, such as lamellae, spheres or cylinders, which depend on the block ratio rather than on the decompression rate or temperature, at least within the rate and temperature ranges investigated in this work. At lower temperatures, however, say below 40 °C, glass transition of the styrene-butadiene diblocks can inhibit independent structure formation while crystallization of their hydrogenated-butadiene analogs can preserve the micellar-solution structure.

Aims: Polyamidoamine (PAMAM) dendrimers with primary amine termini have been extensively explored as drug and gene carriers owing to their unique properties, but their amine-carried cationic charges cause nonspecific cellular uptakes, systemic toxicity and other severe problems in in vivo applications. Method: In this article, we report a charge-reversal approach that latently deactivates PAMAM’s primary amines to negatively charged acid-labile amides in order to inhibit its nonspecific interaction with cells, but regenerates the active PAMAM once in acidic environments. Results: A cascade cancer cell nuclear drug delivery was achieved using the latently amidized PAMAM as the carrier conjugated with folic acid as the targeting group and a DNA-toxin drug camptothecin. The conjugate had low nonspecific interactions with cells, but easily entered cancer cells overexpressing folate receptors via receptor-mediated endocytosis. Subsequently, the endocytosed conjugate was transferred to acidic lysosomes, wherein the active PAMAM carrier was regenerated, escaped from the lysosome and then entered the nucleus for drug release. Conclusion: This reversible deactivation/activation makes PAMAM dendrimers useful nanocarriers for in vivo cancer cell nuclear-targeted drug delivery.

Micelles of hydrophilic−hydrophobic block copolymers, such as poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL), are useful for delivery of hydrophobic drugs. Such micelles can be formed by liquid solvent displacement or dialysis. A more recent approach is to use supercritical fluids as solvents, but the selection criteria for solvents are not well understood. The compressible solvents studied in this work can induce pressure-tunable micellization of PEG-b-PCL. Their capacity and selectivity, and hence their ability to form micelles, depends on their density, polarity, and hydrogen bonding potential. By mixing two solvent components, such as dimethyl ether (good solvent) and trifluoromethane (selective antisolvent), one can control not only the micellization temperature and pressure, but also the bulk separation pressure (cloud pressure), crystallization temperature, and melting temperature. This can be utilized to develop efficient ways to prepare micellar precursors for drug-loaded nanoparticles.

Curcumin has been shown highly cytotoxic towards various cancer cell lines, but its water-insolubility and instability make its bioavailability exceedingly low and thus it generally demonstrates low anticancer activity in in vivo tests. Herein, we report a novel type of polymer-drug conjugates — the high molecular weight curcumin polymers (polycurcumins) made by condensation polymerization of curcumin. The polycurcumins as backbone-type conjugates have advantages of high drug loading efficiency, fixed drug loading contents, stabilized curcumin in their backbones, and tailored water-solubility. The polycurcumins may have many potential applications and their antitumor activities are investigated in this work. The polycurcumins are cytotoxic to cancer cells, but a polyacetal-based polycurcumin (PCurc 8) is highly cytotoxic to SKOV-3, OVCAR-3 ovarian cancers, and MCF-7 breast cancer cell lines. It can be quickly taken up by cancer cells into their lysosomes, where PCurc 8 hydrolyzes and releases active curcumin. It arrests SKOV-3 cell cycle at G0/G1 phase in vitro and induces cell apoptosis partially through the caspase-3 dependent pathway. In vivo, intravenously (i.v.) injected PCurc 8 shows remarkable antitumor activity in SKOV-3 intraperitoneal (i.p.) xenograft tumor model.

Micelles formed through the self-assembly of block copolymers have been widely used to encapsulate highly hydrophobic drugs to increase their effective solubility. However, this emerging nanoparticle technology faces fabrication challenges that call for better understanding of the underlying principles that result in effective micelle-based drug delivery systems. Among the challenges, for example, are how to consistently prepare micelles with a narrow, predictable size-distribution and a high drug loading content, which remain stable upon dilution but dissociate upon reaching the target, and how to design drug carriers that can overcome drug resistance, which is the ultimate cause of cancer patient deaths. Specifically, drug carriers are needed that can simultaneously overcome the membrane-associated multidrug-drug resistance and the intracellular drug resistance.

Molecular dynamics of polyisoprene, polystyrene and poly(styrene-b-isoprene) diblock copolymer has been studied by means of broadband dielectric and magnetic resonance spectroscopies. The measurements of dielectric permittivity as well as NMR second moment, spin–lattice relaxation times T 1 and T 1 ρ in wide range of temperature were performed. It was found that the copolymer exhibits all motions observed in the neat components i.e., three motions connected with polyisoprene blocks (segmental, normal-mode and methyl group rotation) and one (segmental) related to polystyrene blocks. The mutual interaction between polystyrene and polyisoprene chains leads to stiffening of polyisoprene blocks and loosening of polystyrene structure. The polyisoprene segmental and normal-mode motions were analyzed in terms of the Havriliak–Negami model and Vogel–Fulcher–Tamman (VFT) relation. Based on NMR spin-diffusion experiment the size of polystyrene domains in copolymer was evaluated and accounts to 9 nm.

DNA-toxin anticancer drugs target nuclear DNA or its associated enzymes to elicit their pharmaceutical effects, but cancer cells have not only membrane-associated but also many intracellular drug-resistance mechanisms that limit their nuclear localization. Thus, delivering such drugs directly to the nucleus would bypass the drug-resistance barriers. The cationic polymer poly(L-lysine) (PLL) is capable of nuclear localization and may be used as a drug carrier for nuclear drug delivery, but its cationic charges make it toxic and cause problems in in-vivo applications. Herein, PLL is used to demonstrate a pH-triggered charge-reversal carrier to solve this problem. PLL's primary amines are amidized as acid-labile β-carboxylic amides (PLL/amide). The negatively charged PLL/amide has a very low toxicity and low interaction with cells and, therefore, may be used in vivo. But once in cancer cells' acidic lysosomes, the acid-labile amides hydrolyze into primary amines. The regenerated PLL escapes from the lysosomes and traverses into the nucleus. A cancer-cell targeted nuclear-localization polymer–drug conjugate has, thereby, been developed by introducing folic-acid targeting groups and an anticancer drug camptothecin (CPT) to PLL/amide (FA-PLL/amide-CPT). The conjugate efficiently enters folate-receptor overexpressing cancer cells and traverses to their nuclei. The CPT conjugated to the carrier by intracellular cleavable disulfide bonds shows much improved cytotoxicity.

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.

Micellar solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in propane are found to exhibit significantly lower cloud pressures than the corresponding hypothetical nonmicellar solutions. Such a cloud-pressure reduction indicates the extent to which micelle formation enhances the apparent diblock solubility in near-critical and hence compressible propane. Concentration-dependent pressure-temperature points beyond which no micelles can be formed, referred to as the micellization end points, are found to depend on the block type, size, and ratio. The cloud-pressure reduction and the micellization end point measured for styrene-diene diblocks in propane should be characteristic of all amphiphilic diblock copolymer solutions that form micelles in compressible solvents.

Polystyrene, polybutadiene, hydrogenated polybutadiene, and styrene diblock copolymers of these homopolymers can form homogenous solutions in compressible solvents, such as propane and propylene, which separate into two bulk phases upon reducing pressure. The cloud and micellization pressures for homopolymer and diblock copolymers are generally found to be higher in propane than in propylene, except for hydrogenated polybutadiene and polystyrene-block-(hydrogenated polybutadiene). Hydrogenated polybutadiene homopolymers and copolymers exhibit relatively pressure-independent crystallization and melting observed in both propane and propylene solutions.

Highly active catalysts mediating atom transfer radical polymerization (ATRP) at low concentrations, therefore requiring no postpolymerization catalyst removal, are highly desirable for wide commer...

Micellar solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in propane are found to exhibit significantly lower cloud pressures than the corresponding hypothetical nonmicellar solutions. Such a cloud-pressure reduction indicates the extent to which micelle formation enhances the apparent diblock solubility in near-critical and hence compressible propane. Concentration-dependent pressure−temperature points beyond which no micelles can be formed, referred to as the micellization end points, are found to depend on the block type, size, and ratio. The cloud-pressure reduction and the micellization end point measured for styrene−diene diblocks in propane should be characteristic of all amphiphilic diblock copolymer solutions that form micelles in compressible solvents.

Polymer nanoparticles are extensively explored as drug carriers but they generally have issues of premature burst drug release, slow cellular uptake, and retention in acidic intracellular compartments. Herein, we report multifunctioning three-layered nanoparticles (3LNPs) that can overcome these problems. The 3LNPs have a poly(e-caprolactone) (PCL) core, a pH-responsive poly[2-(N,N-diethylamino)ethyl methacrylate](PDEA) middle layer and a polyethylene glycol (PEG) outer layer. The pH-responsive PDEA layer is insoluble at pH above 7 but becomes positively charged and soluble via protonation at pH lower than 6.5. Thus, this layer has three functions: it covers on the PCL core inhibiting the premature burst drug release at the physiological pH, becomes positively charged and thus promotes endocytosis for fast cellular internalization in the acidic interstitium of solid tumors, and is highly positively charged in lysosomes to disrupt the lysosomal membrane and release the nanoparticle into the cytosol. The multifunctioning nanoparticles are an efficient carrier for cancer cytosolic drug delivery. © 2008 American Institute of Chemical Engineers AIChE J, 2008

We present a lattice Monte Carlo study of a series of block copolymer chains in selective solvents of varying quality, first using a diblock chain of the length of N = 32 with a 16–16 microarchitecture, and then – two multiblock chains of N = 64 and N = 128 , with ( 8 – 8 ) 4 and ( 16 – 16 ) 4 microarchitectures, respectively. We report a variety of thermodynamic and structural properties, such as energy, specific heat, end-to-end distance and radius of gyration both for the whole chain and for individual blocks. The simulations have demonstrated that a multiblock copolymer in a selective solvent exhibits protein-like behavior undergoing a two-step transition, first from a swollen state to a secondary ‘pearl-necklace’ state and then to a tertiary super-globular state as the solvent quality decreases, i.e. upon cooling. We have found that mean-squared end-to-end distances of multiblock chains decrease as the temperature is reduced, as expected.

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.

With a lattice Monte Carlo method, we investigate 16−16 symmetric diblock in selective solvent, A-b-B/A, at 10 volume fractions from 1.0 to 0.1, and for each volume fraction, we perform simulations at up to 54 temperatures, using simulation boxes of different sizes. We report temperature dependencies for a number of quantities such as energy, specific heat, and mean-squared end-to-end distances and construct a phase diagram using the thermodynamic and structural quantities as well as snapshots of the selected configurations. The simulated phase diagram is compared with the experimental data of Lodge and co-workers for nearly symmetric poly(styrene-b-isoprene) mixed with dimethyl phthalate.

A low-pressure Carbon Filter Process (patent pending) is proposed to capture carbon dioxide (CO2) from flue gas. This filter is filled with a low-cost carbonaceous sorbent, such as activated carbon or charcoal, which has a high affinity (and, hence, high capacity) to CO2 but not to nitrogen (N2). This, in turn, leads to a high CO2/N2 selectivity, especially at low pressures. The Carbon Filter Process proposed in this work can recover at least 90% of flue-gas CO2 of 90%+ purity at a fraction of the cost normally associated with the conventional amine absorption process. The Carbon Filter Process requires neither expensive materials nor flue-gas compression or refrigeration, and it is easy to heat integrate with an existing or grassroots power plant without affecting the cost of the produced electricity too much. An abundant supply of low-cost CO2 from electricity producers is good news for enhanced oil recovery (EOR) and enhanced coal-bed methane recovery (ECBMR) operators, because it will lead to higher o...

Thermoresponsive polymers have many biomedical applications, but their nondegradability limits their in vivo applications. Herein, we report a new type of degradable thermoresponsive polymers—degradable poly (ethylene glycol) analogues (DPEGs) having lower critical solution temperatures (LCSTs) ranging 10–50°C. DPEGs were synthesized by condensation polymerization of PEG-di(meth)acrylates (PEGDA or PEGDMA) with dithiols. Their LCSTs could be easily tuned by the PEG-chain length and the types of the double bond in the PEG monomers and dithiols. Long PEG chain and the presence of hydrophilic groups in the dithiol monomer increased the LCST of the resulting DPEG. Crosslinking DPEG chains produced thermoresponsive hydrogels. The hydrogels prepared by the end-capping method maintained the thermoresponsive properties of the linear DPEG. The degradable thermoresponsive DPEGs and their hydrogels have great potentials for in vivo biomedical applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008

Polystyrene, polybutadiene, polyisoprene, and their diblock copolymers can form compressible homogeneous solutions in propane that separate upon decompression into a solvent-rich phase and a polymer-rich phase. If the styrene block is large enough, the diblock copolymers can also form a pressure-tunable micellar nanophase that exists below the micellization pressure but above the cloud-point pressure. The onset of micellization and cloud-point transitions can be realistically estimated within a statistical associating fluid theory (SAFT1) framework using universal SAFT1 parameters characteristic of the segment volumes and segment energies, except for the segment-segment interaction energy between the two blocks, which requires an adjustment to account for different types of cloud-point and micellar transitions.

The CO 2 solubility in two ammonium-based polymerized ionic liquids, poly( p -vinylbenzyltrimethyl ammonium tetrafluoroborate), P[VBTMA][BF 4 ], and poly([2-(methacryloyloxy)ethyl] trimethyl ammonium tetrafluoroborate), P[MATMA][BF 4 ], up to 75 °C and 15 bar, is found to be higher than that in bisphenol-A polysulfone. The CO 2 solubility in P[VBTMA][BF 4 ] is found to be higher than that in P[MATMA][BF 4 ] at the same temperature and pressure.

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.

The mechanical strength of polymeric membranes is one of the limitations in their applications. Carbon nanotubes (CNTs) are very effective in reinforcing polymeric materials, but it is unknown whether they degrade the membranes’ gas separation performance. Using brominated poly(2,6-diphenyl-1,4-phenylene oxide) (BPPOdp) as an example, we show that pristine single-wall CNTs (SWNTs) and multi-wall CNTs (MWNTs) formed polymeric nanocomposite membranes with BPPOdp. The composite membranes had an increased CO2 permeability but a similar CO2/N2 selectivity compared to the corresponding pure-polymer membrane. The CO2 permeability increased with increasing the CNT content and reached a maximum of 155 Barrer at 9 wt% of SWNTs, or 148 Barrer at 5 wt% of MWNTs. The CO2/N2 separation performance was insensitive to the MWNT diameter or length. Carboxylic acid-functionalized SWNTs (COOH-SWNTs) dispersed more uniformly in BPPOdp, and neither increased the gas permeability nor deteriorated the gas separation performance. Thus, it is feasible to add CNTs to polymeric membranes for improved mechanical strength without deteriorating the gas separation performance of the membranes. The pristine CNT-enhanced gas permeability was attributed to the formed nanogaps surrounding the CNTs.

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.

Silica-impregnated, brominated PPO [poly(phenylene oxide)] (BPPO) membranes exhibit enhanced CO2 permeability relative to pure BPPO membranes due to higher gas solubility and especially higher gas diffusivity. Among the three silica sizes (2, 10, and 30 nm) characterized in this work, the 10 nm silica is found to result in the highest gas permeability, about 5 times higher than that of the pure BPPO membranes. These permeability enhancements do not cause an appreciable loss of selectivity, which remains essentially unchanged, for example, about 21 for the CO2/N2 separation and about 15 for the CO2/CH4 separation. The permeability increases with increasing silica content, which, however, cannot exceed about 0.35 silica/BPPO weight ratio due to a substantial increase in brittleness.

Laboratory studies of the effect of oxygen content in CO2 on the minimum miscibility pressure (MMP) are conducted on the n-C5H12/n-C16H34 model oil and Cottonwood Creek crude oil with three injection gases of different oxygen contents. The results indicate that the MMPs for these oils increase unfavorably with increasing O2 concentration in the CO2 stream. The experimental results are also supported by our modeling work using a multiple-mixing-cell model, which is found to capture the effects of compositions and temperature, and is found to be a robust and predictive method for determining the MMP. Our experiments and calculations indicate that the effect of O2 contamination on the MMP is larger for heavier oil and the effect of N2 impurity on the MMP is larger than that of O2 impurity.

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.