Thermo‐Rheology of a Proline‐Based Surface‐Active Ionic Liquid: Mixtures with Water and n‐Octane

Surfactant flooding is one of the most promising techniques to recover oil from unprofitable reservoirs. Surface‐active ionic liquids can overcome the limitations of the current surfactants. The rheology of the injecting solutions and the formed slugs is critical in the evaluation of an enhanced oil recovery process. The thermo‐rheological behavior of a biodegradable surface‐active ionic liquid, [ProC₄]DS, and the corresponding binary and ternary mixtures with water and n‐octane was studied. All flow curves exhibited shear‐thinning and thixotropic behavior. The viscoelastic behavior of the ternary samples depended strongly on the [ProC₄]DS content. Three different regions were identified: typical liquid‐like behavior, weak gel, and true gel. The thermal profiles indicated that the tested systems were fully thermoreversible.     

Non‐Ionic,Poly(ethylene oxide)‐Based Surfactants as Intercalants/Dispersants/Exfoliants for Poly(propylene)‐Clay Nanocomposites

Summary: Poly(propylene) (PP)‐clay nanocomposites were prepared from unmodified montmorillonite clays (NaMMT), with poly(ethylene oxide)‐based nonionic surfactants as dispersants/intercalants/exfoliants. The primary objective of this research was to find dispersants that (a) allow PP nanocomposites to be formed by direct melt mixing; (b) are effective with unmodified clays and (c) comprise of only a minor component with respect to both the clay and the overall composition. Linear, branched, gemini and sugar‐based surfactants and structures containing poly(dimethyl siloxane) and poly(methyl methacrylate) blocks were examined. These additives were found to be effective in breaking down the clay agglomerates to tactoids, giving some expansion of the clay structure and partial exfoliation and providing substantially improved clay dispersion. The properties of the derived nanocomposites depend on the level of additive and its structure. Tensile and impact properties show significant improvement over the precursor PP. Also notable are the significantly better thermal and thermo‐oxidative stabilities, as compared to both PP and “clay alone” composites. For optimal properties, it is both necessary and desirable that the surfactant should only be a minor constituent (20–50%) of the composition, with respect to the clay. A preferred surfactant is linear PE‐block‐PEO, with a short PEO block and an alkyl chain with approximately 30 carbon atoms (C₃₀).

     

Recycling Chiral Imidazolidin‐4‐one Catalyst for Asymmetric Diels–Alder Reactions: Screening of Various Ionic Liquids

Various imidazolium ionic liquids such as [Bmim]PF₆, [Bmim]SbF₆, [Bmim]OTf and [Bmim]BF₄ were screened for recycling an organic catalyst [(5S)‐5‐benzyl‐2,2,3‐trimethylimidazolidin‐4‐one ( 1 )] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF₆ or [Bmim]SbF₆. However, reactions in [Bmim]OTf or [Bmim]BF₄ gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

Plasmonic‐enhanced visible‐light‐driven photocatalytic activity of Ag–AgBr synthesized in reactable ionic liquid

BACKGROUND: Plasmonic photocatalysts have attracted considerable attention because of their applications in the degradation of organic pollutants. In order to enhance the stability of AgX photocatalyst, Ag/AgCl, Ag/AgBr/WO₃, and Ag@AgCl/RGO were developed. Results implied that silver halides could maintain stability if the metal Ag was well dispersed on the silver halide particles and could display high catalytic activity. RESULTS: PVP acted as a structure‐directing agent, and a reducing reagent in the reaction. Results show that Ag–AgBr delivered a much higher photocatalytic activity than AgBr and Ag–AgCl. The high photocatalytic activity of the Ag–AgBr composites can be attributed to the presence of metal Ag and the smaller particle size of the samples. The photocatalytic reaction followed first‐order kinetics. The rate constant k for the degradation of MO by Ag–AgBr was 2 and 18 times higher than that of AgBr and Ag–AgCl, respectively. CONCLUSIONS: The MO degradation efficiency of Ag–AgBr was 94% after 10 min. After 5 cycles of repeatability tests, the degradation efficiency of MO still remained at 90%. The high photocatalytic activity of the Ag–AgBr composites can be attributed to the presence of metal Ag and the smaller particle size of the samples. Copyright © 2012 Society of Chemical Industry     

High Stiffness Cellulose Fibers from Low Molecular Weight Microcrystalline Cellulose Solutions Using DMSO as Co‐Solvent with Ionic Liquid

There is a need to develop high‐performance cellulose fibers as sustainable replacements for glass fibers, and as alternative precursors for carbon filaments. Traditional fiber spinning uses toxic solvents, but in this study, by using dimethyl sulfoxide (DMSO) as a co‐solvent with an ionic liquid, a novel high‐performance fiber with exceptional mechanical properties is produced. This involves a one‐step dissolution, and cost‐effective route to convert high concentrations of low molecular weight microcrystalline cellulose into high stiffness cellulose fibers. As the cellulose concentration increases from 20.8 to 23.6 wt%, strong optically anisotropic patterns appear for cellulose solutions, and the clearing temperature (T _c) increases from ≈100 °C to above 105 °C. Highly aligned, stiff cellulose fibers are dry‐jet wet spun from 20.8 and 23.6 wt% cellulose/1‐ethyl‐3‐methylimidazolium diethyl phosphate/DMSO solutions, with a Young's modulus of up to ≈41 GPa. The significant alignment of cellulose chains along the fiber axis is confirmed by scanning electron microscopy, wide‐angle X‐ray diffraction, and powder X‐ray diffraction. This process presents a new route to convert high concentrations of low molecular weight cellulose into high stiffness fibers, while significantly reducing the processing time and cost.     

High Regioselective Diels–‐Alder Reaction of Myrcene with Acrolein Catalyzed by Zinc‐Containing Ionic Liquids

The ambient zinc‐containing ionic liquids, MX‐ZnCl₂, functioning as both Lewis acid catalyst and green solvent, are employed for a high regioselective Diels–Alder reaction of myrcene with acrolein for the first time, where MX is either 1‐butyl‐3‐methylimidazolium chloride (BmimCl), 1‐ethyl‐3‐methylimidazolium bromide (EmimBr), N‐butylpyridinium bromide (BPyBr), or N‐ethylpyridinium bromide (EtPyBr). Compared with the analogous reaction performed over a ZnCl₂ catalyst in the conventional solvent dichloromethane, higher regioselectivity of the ‘para’ cycloadduct and excellent yield were achieved at shorter reaction time in these ionic liquids with optimized molar compositions of MX and ZnCl₂. These moisture‐insensitive ionic liquids can be easily separated from reaction products after simple washing with hexane, allowing their reuse with no obvious loss in activity.     

Co‐administration of Antimicrobial Peptides Enhances Toll‐like Receptor 4 Antagonist Activity of a Synthetic Glycolipid

This study examines the effect of co‐administration of antimicrobial peptides and the synthetic glycolipid FP7, which is active in inhibiting inflammatory cytokine production caused by TLR4 activation and signaling. The co‐administration of two lipopolysaccharide (LPS)‐neutralizing peptides (a cecropin A–melittin hybrid peptide and a human cathelicidin) enhances by an order of magnitude the potency of FP7 in blocking the TLR4 signal. Interestingly, this is not an additional effect of LPS neutralization by peptides, because it also occurs if cells are stimulated by the plant lectin phytohemagglutinin, a non‐LPS TLR4 agonist. Our data suggest a dual mechanism of action for the peptides, not exclusively based on LPS binding and neutralization, but also on a direct effect on the LPS‐binding proteins of the TLR4 receptor complex. NMR experiments in solution show that peptide addition changes the aggregation state of FP7, promoting the formation of larger micelles. These results suggest a relationship between the aggregation state of lipid A‐like ligands and the type and intensity of the TLR4 response.     

Detergency of Vegetable Oils and Semi‐Solid Fats Using Microemulsion Mixtures of Anionic Extended Surfactants: The HLD Concept and Cold Water Applications

In spite of the increasing interest in cold temperature detergency of vegetable oils and fats, very limited research has been published on this topic. Extended surfactants have recently been shown to produce very promising detergency with vegetable oils at ambient temperature. However, the excessive salinity requirement (4–14 %) for these surfactants has limited their use in practical applications. In this work, we investigated the mixture of a linear C₁₀–18PO–2EO–NaSO₄ extended surfactant and a hydrophobic twin‐tailed sodium dioctyl sulfosuccinate surfactant for cold temperature detergency of vegetable oils and semi‐solid fats. Four vegetable oils of varying melting points (from ?10 to 28 °C) were studied, these were canola, jojoba, coconut and palm kernel oils. Anionic surfactant mixtures showed synergism in detergency performance compared to single surfactant systems. At temperatures above the melting point, greater than 90 % detergency was achieved at 0.5 % NaCl. While detergency performance decreased at temperatures below the melting point, it was still superior to that of a commercial detergent (up to 80 vs. 40 %). Further, results show that the experimental microemulsion phase behaviors correlated very well with predictions from the hydrophilic–lipophilic deviation concept.     

Correlating structure with ionic conductivity in bis(phosphonium)‐containing [NTf2] thiol–ene networks

Thiol–ene photopolymerization was employed in order to prepare a series of covalently crosslinked bis(phosphonium)‐containing poly(ionic liquid) (PIL) networks. While the counteranion was held constant (NTf₂), the structure of the bis(phosphonium)‐containing ‘ene’ monomer was varied in order to explore the breadth of thermal, mechanical and conductive properties available for this system. Towards this end, it was determined that more flexible spacers within the cationic monomer led to PIL networks with lower T_g values and higher conductivities. Most notable was a two‐ to three‐orders‐of‐magnitude increase in ionic conductivity (from 10^?9 to 10^?6 S cm^?1 at 30 °C, 30% relative humidity) when the R group on phosphonium was changed from phenyl to isopropyl. Changing the functional group ratio to off‐stoichiometry also led to a slight increase in conductivity. Although the thermal stability (T_d5%) of the phosphonium ionic liquid monomers was found to be significantly higher (>400 °C) than that of analogous imidazolium monomers, this improvement was not observed to directly transfer over to the polymer where a two‐step decomposition pathway was observed. The first step is attributed to the thiol monomer backbone while the second step correlates well with decomposition of the phosphonium portion of the PIL. © 2019 Society of Chemical Industry     

Synergisms in Binary Mixtures of Anionic and pH‐Insensitive Zwitterionic Surfactants and Their Precipitation Behavior with Calcium Ions

This work aims to investigate synergy in anionic and zwitterionic surfactant mixtures, as they result in better interfacial properties and micellization behavior. Various mixtures of the pH‐insensitive zwitterionic surfactant 3‐(decyldimethylammonio) propanesulfonate (Zwittergent 3–10) and sodium dodecylsulfate (SDS) were prepared in aqueous solution at a range of pH values between 2 and 13. The thermodynamic parameters during mixed surfactant adsorption at the air/water interface are obtained and the results show the mixed surfactant systems having superior properties to the constituent surfactants. Experimentally, the mixed surfactant solutions clearly improve the surface activities by lowering the critical micelle concentration (CMC) and lowering the surface tension at the air/water interface. The synergisms are investigated through the interaction parameters estimated from regular solution theory that is used to quantitatively describe the nonideality of surfactant mixtures. High negative interaction parameters are obtained from these surfactant mixtures. Experimental precipitation phase boundaries of SDS in the presence of CaCl₂ were also investigated in mixtures containing pH‐insensitive zwitterionic surfactant at different pH levels from 2 to 13 and SDS mole fractions of 0.25, 0.50, 0.75, and 1.00. Changes in the precipitation phase boundaries are due to the changes in the speciation or activities of the major components both below and above the CMC. As a result, the precipitation phase boundaries are pH dependent. In addition, mixed micellization and counterion binding to the micelle also change the precipitation phase boundary above the CMC. The activity‐based solubility product of calcium dodecylsulfate is also determined from the precipitation phase boundaries below the CMC. X‐ray diffraction patterns and SEM images confirm that only calcium dodecylsulfate precipitates in the soap scum for all pH and surfactant compositions studied.     

Alkylation of Ammonium Salts Catalyzed by Imidazolium‐Based Ionic Liquid Catalysts

Quaternary ammonium salts were synthesized from ammonium salts and dialkyl carbonates over imidazolium ionic liquid catalysts. The reaction gave almost stoichiometric amounts of the quaternary ammonium salts for halides and nitrates. It was found that the electron‐donating property of the alkyl moieties of ammonium cations, the electrophilic nature of the alkyl group of the carbonate, the acidity of the acid that the anion of the ammonium salt corresponds to, and the steric hindrance of the ammonium salts and the dialkyl carbonates are the key factors that influence the yields of quaternary ammonium salts. Strong electron‐donating alkyl groups on the nitrogen atom of the ammonium salt, electron‐withdrawing groups on the methylene carbon of dialkyl carbonate, and weaker steric hindrance of the starting ammonium salts and dialkyl carbonates favor the alkylation reaction of ammonium salts.     

Recyclable Copper Catalysts Based on Imidazolium‐Tagged Bis(oxazolines): A Marked Enhancement in Rate and Enantioselectivity for Diels–Alder Reactions in Ionic Liquid

Imidazolium‐tagged bis(oxazolines) have been prepared and used as chiral ligands in the copper(II )‐catalysed Diels–Alder reaction of N‐acryloyl‐ and N‐crotonoyloxazolidinones with cyclopentadiene and 1,3‐cyclohexadiene in the ionic liquid 1‐ethyl‐3‐methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [emim][NTf₂]. A significant and substantial enhancement in the rate and enantioselectivity was achieved in [emim][NTf₂] compared with dichloromethane. For example, complete conversion and enantioselectivities up to 95 % were obtained for the reaction between N‐acryloyloxazolidinone and cyclopentadiene within 2 min in [emim][NTf₂] whereas the corresponding reaction in dichloromethane required 60 min to reach completion and gave an ee of only 16 %. The enhanced rates obtained in the ionic liquid enabled a catalyst loading as low as 0.5 mol % to give complete conversion within 2 min while retaining the same level of enantioselectivity. The imidazolium‐tagged catalysts can be recycled ten times without any loss in activity or enantioselectivity and showed much higher affinity for the ionic liquid phase during the recycle procedure than the analogous uncharged ligand.     

Liquid–liquid extraction of a recombinant protein with reverse micelles

Recombinant cytochrome b₅ was extracted into the reversed micelle phase of an anionic surfactant (AOT) in octane and back-extracted to a final aqueous phase. The extraction of the protein was controlled by an electrostatic mechanism, since it was dependent on the global charge of the protein. This was directly demonstrated by experiments with native and mutant cytochromes obtained by site directed mutagenesis. The back-extraction of cytochrome b₅ to a fresh aqueous phase was decreased by factors that reduced the size of the water pool of the organic phase, such as high salt concentrations (1–2 mol dm^?3 NaCl) and low temperatures (4°C), probably because of an increase in a favourable interaction of this protein with the surfactant at closer distances.     

Morphology evolution of a thermotropic liquid‐crystalline polymer in a polyamide 6,6 matrix regulated by graphene

A two‐step process, thermotropic liquid‐crystalline polymer (TLCP) premixing with reduced graphene oxide (RGO) followed by blending with polyamide 6,6 (PA66), was used to prepare ternary TLCP/RGO/PA66 blends. The rheological behaviors, morphology, and mechanical properties of the blends were investigated. The results show that RGO migrated from the TLCP phase to the interface between the TLCP and PA66 phase during melt blending; this was due to a similar affinity of the RGO nanosheets to both component polymers. The dimensions of the dispersive TLCP domains were markedly reduced with the mounting RGO content; this revealed a good compatibilization effect of RGO on the immiscible polymers. The hierarchical structures of the TLCP fibrils were found in both the unfilled TLCP/PA66 blends and TLCP/RGO/PA66 blends. This supposedly resulted from the extensional and torsional action of unstable capillary flow. With the addition of RGO, the viscosities of the blends decreased further, and the fibrillation of TLCP and the mechanical performance of TLCP composites were both enhanced. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43735.     

Lipase immobilization on ionic liquid‐modified magnetic nanoparticles: Ionic liquids controlled esters hydrolysis at oil–water interface

Ester hydrolysis at oil–water interface by lipase covalently immobilized on ionic liquid‐modified magnetic nanoparticles was investigated. Magnetic supports with a diameter of 10–15 nm were synthesized by covalent binding of ionic liquids (chain length C₄ and C₈ and anions Cl^?, BF₄^?, and PF₆^?) on the surface of Fe₃O₄ nanoparticles. Lipase was covalently immobilized on Fe₃O₄ nanoparticles using ionic liquids as the coupling reagent. Ionic liquid‐modified magnetic nanoparticle‐grafted lipase preferentially located at the oil–water interface. It has higher catalytic activity than its native counterpart. A modified Michaelis–Menten model was used to elucidate the effect of stirring rate, aqueous–organic phase ratio, total amount of enzyme, and ester chain length. The influences of these conditions on esters hydrolysis at oil–water interface were consistent with the introduction of the ionic liquids interlayer. Ionic liquids could be used to control the oil–water interfacial characteristics during lipase catalyzed hydrolysis, and thus control the behavior of immobilized lipase. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Metal Triflate‐Catalyzed Regio‐ and Stereoselective Friedel–Crafts Alkenylation of Arenes with Alkynes in an Ionic Liquid: Scope and Mechanism

In the metal triflate‐catalyzed hydroarylation of alkynes, employing an ionic liquid dramatically enhanced the catalytic activities, resulting in broadening the scope of substrates (arenes and alkynes). In some cases, even reactions that were not possible in conventional organic solvents proceeded smoothly in ionic liquids. Moreover, the ionic liquid phase containing catalyst could be readily recovered by simple decantation of the organic layer after reaction and reused for the following runs without any significant loss of activity. Mechanistic studies including ¹³C NMR analysis of reaction intermediates and isotope experiments confirmed for the first time that this type of reaction proceeds via vinyl cationic intermediates.     

Effect of operation conditions in the pervaporation of ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) is known to show preferential permeation of ethanol in the pervaporation of ethanol–water mixture. Although this polymer presents good characteristics for the separation of organic–water solutions, operation conditions and membrane characteristics, such as thickness, affect its pervaporation performance. The effect of temperature and feed concentration on pervaporation was studied. During pervaporation of 10 wt % ethanol–water solution, the separation factor (α_H2O^EtOH) remains almost constant, whereas the permeation flux (F) increases exponentially with operation temperature. On the other hand, the separation factor decreases, whereas the permeation flux increases with ethanol content in the feed mixture. The membrane thickness also affects the performance of PTMSP polymer films: selectivity increases sharply with membrane thickness up to 50 μm, whereas it remains constant for thicker membranes. The permeation flux decreases with membrane thickness in the whole range studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:1395–1403, 2004     

Imidazolium‐Based Ionic Liquid as Modulator of Physicochemical Properties of Cationic,Anionic, Nonionic,and Gemini Surfactants

The aggregation morphology of 2 cationic surfactants (cetyldimethylethanolammonium bromide and cetyldiethylethanolammonium bromide), an anionic surfactant (sodium dodecylbenzenesulfonate), a nonionic surfactant (Triton X‐100), and 2 gemini surfactants (16‐4‐16,2Br^?[butanediyi‐1,4‐bis(dimethyldohexylammonium bromide)] and 16‐6‐16,2Br^?[hexanediyi‐1,6‐bis(dimethyldohexylammonium bromide)]) in the presence of the ionic liquid (IL) 1‐ethyl‐3‐methylimidazoliumbromide [Emim][Br] is studied using various techniques such as surface tension, conductivity, and UV–visible and fluorescence spectroscopy. Increasing the concentration of [Emim][Br] results in a decrease in the critical micelle concentration (CMC) value of the surfactants. Various interfacial properties, namely the surface excess concentration (Г_max), minimum area per molecule at the air–water interface (A_min)_, and surface pressure at the CMC (π_cmc), as well as the thermodynamic parameters such as free energy of the given air/water interface (), Gibbs free energy of micelle formation (), Gibbs free energy of micellization per alkyl tail (), Gibbs energy of transfer (), and standard free energy of adsorption () were also investigated. The aggregation number (N_agg) was determined by the fluorescence method. It was observed that N_agg decreased with increasing weight‐percent of the IL.