Excellent Interfacial Activity Research Articles

Two-step synthesis of ionic liquid demulsifiers for demulsification of water-in-oil emulsion

Stabilized water-in-oil emulsions present significant challenges for oil production. However, current demulsifiers often face limitations such as high demulsification temperatures, low efficiencies, and complex synthesis processes, making the resolution of this challenge a demanding task. In this study, we successfully synthesized two ionic liquid demulsifiers, PEDA-Br and GEDA-Br, employing a straightforward two-step procedure. The objective was to enable effective treatment of water-in-oil emulsions at low temperatures with high efficiency. The structure of the demulsifiers was characterized utilizing Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectra (1H NMR). Bottle tests were then conducted to evaluate their demulsification efficiency (DE) in water-in-oil (W/O) emulsions. The results demonstrated that GEDA-Br achieved a DE of 98.92 % at a concentration of 500 mg/L and a temperature of 50 °C after 2 h. Additionally, both PEDA-Br and GEDA-Br exhibited DE values exceeding 95 % at a salinity level of 10,000 mg/L, and both proved effective across a broad pH range of 4 to 12. These findings highlight their robust resistance to high salinity and both acidic and alkaline conditions. The study also examined the demulsification mechanism in terms of interfacial tension (IFT), elastic modulus of the interfacial film, three-phase contact angle (TCA), and microscopic observations. The excellent interfacial activity, ability to reduce interfacial tension, and electrostatic neutralization capability are responsible for its outstanding demulsification performance.

Correlation study between structural parameters of droplets and rheological properties of O/W high internal phase Pickering emulsions above the closest packing density

The correlation between the structural parameters of droplets and rheological properties of O/W high internal phase Pickering emulsions (HIPPEs) stabilized by soy protein isolate (SPI) nanoparticles was elucidated, with a volume fraction of dispersed phase (ϕ) above the closest packing density (74%). The structural basis of SPI nanoparticles was confirmed to be spherical heat-induced protein aggregates, which had moderate wettability and excellent interfacial activity. The structural parameters of emulsion droplets (contact length L, diameter D, length d1, width d2, the number of adjacent contact droplets Z), and the stability and rheological properties of HIPPEs were characterized by the confocal laser scanning microscopy (CLSM), diffusing wave spectroscopy (DWS), and mechanical rheometer respectively. The results of CLSM indicated the transition of droplets from spherical to polyhedral shapes as increased ϕ, accompanied by an increased L and Z. The rheological and stability analysis confirmed the widened linear viscoelastic range, elevated gel point (εc), and the extended half−life of the intensity autocorrelation function of HIPPEs as ϕ increased. Moreover, the loss factor (tan δ) remained constant at 0.1 within the ϕ of 74%–86%, revealing the solid−like nature of HIPPEs. The correlation between ϕ, structural parameters of droplets, and rheological properties of HIPPEs was further analyzed. The nonlinear regression fitting between the L/D and G' (elastic modulus) yielded a better fitting effect than d1/d2 and Z, suggesting an intrinsic correlation between emulsion structure and rheology. In summary, this study elucidated the intricate relationship between ϕ, droplet structure, and rheological properties of HIPPEs, offering a research foundation and theoretical basis for the development and application of protein particle−stabilized HIPPEs.

Water/oil interfacial behaviors of soy hull polysaccharide revealed by molecular dynamics simulation and particle tracking microrheology

The soy hull polysaccharide (SHP) exhibits excellent interfacial activity and holds potential as an emulsifier for emulsions. To reveal the behavior of SHP at the water/oil (W/O) interface in situ, molecular dynamics (MD) simulations and particle tracking microrheology were used in this study. The results of MD reveal that SHP molecular spontaneously move toward the interface and rhamnogalacturonan-I initiates this movement, while its galacturonic acids on it act as anchors to immobilize the SHP molecules at the W/O interface. Microrheology results suggest that SHP forms microgels at the W/O interface, with the lattices of the microgels continually undergoing dynamic changes. At low concentrations of SHP and short interfacial formation time, the network of the microgels is weak and dominated by viscous properties. However, when SHP reaches 0.75 % and the interfacial formation time is about 60 min, the microgels show perfect elasticity, which is beneficial for stabilizing emulsions.

Dumbbell-shaped polymeric nanoparticles with one-side anchored Pd-clusters for efficient catalytic hydrogenation at biphasic interfaces

Pickering interfacial catalysts incorporated with amphiphilic architecture significantly expand the sustainability of green catalysis systems. In this work, we present precise and well-designed dumbbell-shaped Janus-structured polymeric nanoparticles with one-side anchored palladium clusters (DB-JPP-Pd) as Pickering interfacial catalyst for static hydrogenations. The large wettability difference of each lobe renders the prominent amphiphilicity of the dumbbell-shaped DB-JPP-Pd. The amphiphilic Janus catalyst displays excellent interfacial activity and extensively reduces the interfacial tension from 34.06 ± 0.13 to 20.54 ± 0.31 mN/m, promoting the formation of a more stable Pickering emulsion than that of the bulk PS-Pd catalyst, which can continuously provide a large interfacial area and shorten the molecular mass transfer distance during the reaction process. As a result, the DB-JPP-Pd catalyzed nitroarene reduction reaction exhibits a normalized reaction rate constant (knor) of 3.39 min−1⋅g−1⋅L under static conditions, which is 56.5 times higher than that of bulk PS-Pd. The constructed Pickering interfacial catalysis (PIC) system converts all the nitrobenzene into aniline within three minutes and possesses excellent selectivity in hydrogenations of different nitro aromatics. In addition, the emulsion catalytic system was conveniently recycled for ten consecutive runs. Hence, this unique amphiphilic dumbbell-shaped catalyst effectively develops an efficient static biphasic catalysis system.

Preparation of surface-active carbon dots with fluorocarbon and hydrocarbon hybrid chains via a one-pot solvothermal technique and their characterization and potential applications

Amphiphilic carbon dots (CDs) are new surface-active materials that exhibit several advantages over conventional small surfactants, such as improved stability and reduced toxicity. However, unlike for conventional small surfactants, amphiphilic CDs that simultaneously exhibit excellent surface and interfacial activities have never been achieved. Herein we prepare new amphiphilic CDs with fluorocarbon and hydrocarbon hybrid hydrophobic chains (FH-CDs) using a facile one-pot solvothermal technique. The obtained FH-CDs showed excellent surface and interfacial activities, and reduced the surface tension at critical micelle concentration and the oil-water interfacial tension to 16.7 and 2.2 mN/m, respectively. Comparison with control CDs bearing only non-hybrid hydrophobic chains demonstrated that decorating CDs with fluorocarbon and hydrocarbon hybrid chains contributed to the excellent interfacial activity, while only fluorocarbon chains contributed to good surface activity. The excellent surface and interfacial activities made FH-CDs good emulsifiers for the formation of stable water-in-oil emulsions and for the preparation of relatively uniform polystyrene spheres via emulsion polymerization. Moreover, FH-CD was a good wetting agent, whose aqueous solution could wet numerous different surfaces, including the commonly non-wettable amphiphobic polytetrafluoroethylene.

Multiscale study of Janus nanosheets’ interfacial activity

As the challenge of enhancing oil recovery from reservoirs continues to grow, it becomes increasingly crucial to seek out new materials for oil displacement. Janus graphene oxide (JGO) with excellent interfacial activity stands out as a promising candidate, which enables it to locate crude oil and effectively displace it towards production wells. One key advantage of JGO is its ability to reduce interfacial tension and create interfacial films, attributed to JGO nanosheets adsorbing at oil–water interfaces. Another noteworthy property of JGO is its capacity to transform oil-wet rock surfaces into water-wet surfaces, which is because JGO nanosheets can interact hydrophobically with crude oil molecules on rock surfaces. In addition, JGO helps mitigate capillary resistance by altering the concave oil–water front to a flat state. Microscopic displacement shows that JGO nanosheets enlarge the sweep efficiency and oil-washing efficiency of water. Nuclear magnetic resonance experiment indicates that JGO nanofluid can increase oil recovery by 17.1 %. This research presents a comprehensive exploration of the interfacial activity of Janus nanofluid, spanning from the molecular scale to the micro and core scales.

General liquid vegetable oil structuring via high internal phase Pickering emulsion stabilized by soy protein isolate nanoparticles

Oil structuring has attracted immense interest in the last decades because it can transform liquid oils into elastic semi-solids, which has been widely used in material science, pharmaceutical industry, and food processing. However, the facile conversion of liquid vegetable oils into soft matters without changing their intrinsic nature is challenging. Here we report a general approach for structuring liquid vegetable oils by a high internal phase Pickering emulsion (HIPPE) stabilized by edible soy protein isolate (SPI) nanoparticles. SPI nanoparticles with moderate amphipathy (θ = 90.7°) and size (∼187 nm) were obtained via the heat-induced aggregation of native SPI. These SPI nanoparticles possessed excellent interfacial activity and emulsion stabilization ability and thus were suitable for preparing edible HIPPEs from diverse liquid vegetable oils. The effect of internal volume fraction (ϕ) and particle concentration, stability, and rheology of Pickering emulsions were studied. Particularly, the role of intrinsic surfactants (e.g., lecithin) in vegetable oils on the interfacial and macro rheology of the system was highlighted. Compared with native SPI, SPI nanoparticles endowed the HIPPEs with improved stability (>14 days), high interfacial pressure (>2 mN/m), and high elastic modulus (>900 Pa). Moreover, the HIPPEs stabilized by SPI nanoparticles exhibited a good ability to structure various vegetable oils, depending on oil types and ϕ. We envisage that this biomass-mediated HIPPE system provides a promising strategy to structure various liquid vegetable oils, significantly facilitating sustainable development.

Synthesis and demulsification performance of a Gemini ionic liquid with dual cationic active centers

Currently, widely-used demulsifiers are primarily produced using ethylene oxide and propylene oxide as raw ingredients. The production process is hazardous and complicated, and the demulsification temperature for crude oil emulsions is typically above 60 ℃. In this work, an efficient Gemini ionic liquid demulsifier (Y12) with dual cationic active centers was prepared using a one-pot synthesis route. The structure of demulsifiers was analyzed by FTIR and 1H NMR spectroscopy. The bottle test was utilized to assess the demulsification performance. The results revealed that the demulsification efficiency (DE) of Y12 could achieve 100 % at a concentration of 400 mg/L under 50 ℃ for 120 min. Emulsion with different oil content were treated with Y12 at different temperatures, the DE of C30 and C70 emulsions reached 100% at temperature of 50 ℃ and 70 ℃, respectively. Furthermore, Y12 exhibited effectiveness across a wide range of pH value and high salinity conditions. To further confirm the demulsification of Y12, some commercial demulsifiers were used for comparison. It was observed that Y12 had better performance than commercial demulsifiers, indicating its promising potential for applications. The demulsification mechanism was investigated through relative solubility numbers (RSN), interfacial tension (IFT), three-phase contact angle (TCA), zeta potential, and coalescence time of water droplets (CTW). Especially, to further investigate the demulsification mechanism of Y12 demulsifier, Y8 and Y16 with different lengths of hydrophobic chains were also prepared and used for comparison. Y12 had an excellent interfacial activity and strong capability of reducing interfacial tension, which facilitates the formation of an unstable composition interfacial film and results in the oil–water separation.

A smart material: Multi-stimulus-responsive composite microspheres prepared via RAFT polymerization as recyclable pickering emulsifiers and their application in stabilizing real oil phases

The development of smart composites to sustainably separate and recover oil from oily water had attracted much attention. In this study, tri-block (P(LMA-b-NIPAM-b-AA)) polymer brushes were controllably “grown on” the Fe3O4 surface by three-step surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization to prepare Fe3O4-P(LMA-b-NIPAM-b-AA) (MNPLNA) magnetic nanospheres with interfacial activity. The MNPLNA nanospheres were characterized to demonstrate the triple response of pH, temperature and magnetism. Meanwhile, the comparison experiments showed that the MNPLNA nanospheres with tri-block structure had excellent interfacial activity. Then, the O/W type of Pickering emulsion was prepared by using MNPLNA nanospheres as the particle emulsifier. The size variation pattern of Pickering emulsion was comprehensively investigated by adjusting the concentration of nanospheres, oil-water ratio, electrolyte concentration and polarity of oil phase. Pickering emulsions were controllably separated by the action of an external magnetic field, and could be reversibly switched at least 10 cycles between emulsified and broken states under the trigger of pH and temperature. In addition, MNPLNA nanospheres exhibited excellent emulsification properties for stabilizing variety of real oil phases (e.g., canola oil, kerosene, diesel and crude oil). Based on this, MNPLNA nanospheres were applied as smart multifunctional materials in simulated kerosene-containing wastewater separation. MNPLNA nanospheres could be used to recover kerosene with high recovery rate after 10 separation cycles under the stepwise action of pH, temperature and magnetic field.

Interaction of crude oil with halogen-free ionic liquid-based catanionic surfactants

Chemical injection has proved to have superior performance in improving oil recovery. The injected chemicals are typically designed to participate in interfacial interactions at liquid–liquid and rock-liquid interfaces while having minimum adsorption onto the rock surface. This study endeavors to investigate the interfacial activity of several environmentally-friendly halogen-free ionic liquid-based catanionic surfactants synthesized via an ion exchange reaction between cationic imidazolium-based ionic liquids, [Cnmim][Cl] (n = 4,8,12), and anionic surfactants, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and dioctyl sodium sulfosuccinate. Results revealed that the catanionic surfactant synthesized with medium-chain ionic liquid (n = 8) and sodium dodecyl sulfate exhibited higher interfacial activity, demonstrating a minimum crude oil-brine interfacial tension of 0.17 mN/m and wettability alteration index of 0.79. The results of the adsorption study also revealed the adsorption density of 2.19 mg/g onto the dolomite surface for 2000 mg/L of catanionic surfactant in seawater, which was considerably lower than cetyltrimethylammonium bromide adsorption (11.55 mg/g) in the control experiment. Finally, the surface energy analysis of liquid-rock interactions was conducted using the concept of work of adhesion to scrutinize the wettability alteration and adsorption processes, where a direct relationship between work of adhesion and adsorption density was proposed. According to the results of this study, medium chain ionic liquid-based catanionic surfactant containing dodecyl sulfate anion, exhibiting excellent interfacial activity and low adsorption tendency onto the dolomite surface, could be considered in future chemical enhanced oil recovery applications.

Interfacial properties of protein nanofibrils with different morphology prepared using aqueous solvent with ethanol: Part I. preparation and characterization

β-lactoglobulin can self-assemble into nano-fibrils with high specific surface area and hydrophobic groups, resulting in excellent interfacial activity. In this paper, β-lactoglobulin fibrils with conformation from semi-flexible to worm-like were prepared by controlling the polarity of the self-assemble precursor solution. The effects of ethanol on the surface properties, microscopic interaction forces and secondary structure of the proteins in the precursor solution, and the morphology, secondary structure, mechanical properties, and surface properties of the formed fibrils were investigated, using techniques including atomic force microscopy, Fourier transform infrared spectroscopy, circular dichroism spectroscopy and molecular dynamic simulation, etc. It was found that with the increase of ethanol concentration in the aqueous solvent, both the fibril length and diameter became smaller, the content of β-sheet in the fibrils gradually decreased whereas the content of random curl increased, resulting in decrease of the modulus of the fibrils (5.47 ± 0.54 GPa for semi-flexible fibrils and 0.52 ± 0.20 GPa for worm-like fibrils). With increasing ethanol concentration, the polarity of the precursor solution decreased, and both hydrophobic interactions and disulfide bonds of the proteins decreased whereas the electrostatic interactions with solvent were enhanced, which resulted in the increase of particle size of the precursor proteins and thus facilitated the final formation of fibrils with worm-like morphology. However the fibrillation process mainly occurs in the heating stage but not in the precursor solution. The surface hydrophobicity of the formed fibrils increased, whereas the amount of free sulfhydryl groups and surface charge decreased slightly with the increase of ethanol concentration. Their effects on the interfacial functional properties will be investigated further.

A new zwitterionic surfactant with high interfacial activity and high salt tolerance derived from methyl oleate through an eco‐friendly aryl‐introducing method

AbstractSurfactants, that can reduce the interfacial tension between crude oil and formation water to ultra‐low, are needed in tertiary oil recovery. A bio‐based zwitterionic surfactant, N‐phenylpropanaldehyde epoxy acetal octadecanoicamido propyl‐N, N‐dimethyl hydroxy sulfonate (PADS), was derived from methyl oleate. In the process of synthesizing PADS, a new reactive site was introduced by epoxidizing methyl oleate and then the benzene ring was introduced by acetalization, which was a greener new method of introducing benzene ring into hydrophobic chains of surfactants. PADS was identified by ESI‐MS and NMR, and its interfacial activity was measured by interfacial tensiometer. The results showed that PADS possessed excellent interfacial activity and potential for low‐dose application. Under alkali‐free conditions, it could reduce the interfacial tension between crude oil and simulated formation water to ultra‐low in a wide concentration range (0.005–3 g/L). In addition, although the NaCl concentration was 230 g/L in the system, PADS still had good interfacial activity and could maintain ultra‐low oil–water interfacial tension. The protocol of epoxidation and acetalization provides a new feasible path to preparing bio‐based surfactants with high interfacial activity.

Experimental investigation of zwitterionic surfactant-based silica nanofluid spontaneous imbibition at high salinity and elevated temperature conditions

High-efficiency development of low permeability reservoirs is significant to maintaining a balance between energy supply and social needs. Surfactant-based nanofluids with an excellent interfacial activity that can penetrate the small throats and narrow pores are considered promising EOR agents. However, the applications of nanofluids in harsh reservoir conditions remain to be challenging due to high stability requirements. In this work, a highly stable active nanofluid that could withstand high salinity (API brine) and elevated temperatures was prepared by mixing zwitterionic hydroxypropyl sulfobetaine surfactant with low-molecular-weight ligand modified silica nanoparticles. At a surfactant/nanoparticle concentration ratio of 0.5, the spontaneous imbibition recovery factor of dodecyl hydroxypropyl sulfobetaine-based nanofluid was 2.61 times higher than API brine, 1.29 times higher than API brine-based nanofluid and 0.37 times higher than surfactant alone. Meanwhile, the impacts of surfactant carbon chain length, permeability as well as hydrochloric acid were included. Experimental results indicated that surfactants with longer carbon chain length would destabilize the nanofluids due to increasing hydrophobic interactions, and nanoparticle aggregation/precipitation would impose adverse impacts on spontaneous imbibition because of pore/throat plugging. Though increasing permeability could partially ease the negative plugging effects, the potential risks should never be overlooked. Properly using hydrochloric acid could greatly enhance the stability of nanoparticles by forming an “H+” protection layer and extend their applications to over 80 °C, but the presence of acid also disturbed the adsorption behaviors of surfactants, therefore, different phenomena were noticed when the nanofluid formula changed. A good spontaneous imbibition system should possess both IFT reduction and wettability alteration capabilities, and nanoparticles’ ability to adsorb and disperse polar compounds such as asphaltene should be fully fulfilled. This study provides new guidance for nanofluid formulation to support the effective development of low-permeability oil reservoirs.

Amine functional cellulose derived from wastepaper toward oily wastewater treatment and its demulsification mechanism

• AWP demulsifier with amphipathicity and interfacial activity was prepared. • Recycling solid wastepaper was used as raw material. • The demulsification performance of AWP in oily wastewater exceeded 99.16%. • AWP could be used in acidic, alkaline or high salt conditions with high efficiency. Removing oil from oily wastewater is critically required prior to industrial production and environmental protection. Recycling of solid waste has received extensive attention from academia because of its economic and environmental benefits to the industry. In this work, an amine-functionalized recycling wastepaper demulsifier (AWP) was prepared and used to treat oily wastewater. The morphology, composition, wettability, and interfacial property were investigated. The results showed that AWP had appropriate amphipathy and excellent interfacial activity. Accordingly, it could adsorb and displace asphaltene at the interface, thus destroying or softening the interfacial film. AWP exhibited an excellent demulsification performance, the light transmittance of separated water and the total degrease rate exceeded 89.6% and 99.16%, respectively. Importantly, AWP could be used under the acidic, alkaline or high salt conditions. This work not only realizes the recycling of waste wastepaper but also provides a new AWP demulsifier for the treatment of oily wastewater.

Tuning Supramolecular Polymers' Amphiphilicity via Host-Guest Interfacial Recognition for Stabilizing Multiple Pickering Emulsions.

Supramolecular host-guest chemistry bridging the adjustable amphiphilicity and macromolecular self-assembly is well advanced in aqueous media. However, the interfacial self-assembled behaviors have not been further exploited. Herein, we designed a β-cyclodextrin-grafted alginate/azobenzene-functionalized dodecyl (Alg-β-CD/AzoC12) supra-amphiphilic system that possessed tunable amphiphilicity by host-guest interfacial self-assembly. Especially, supra-amphiphilic aggregates could be utilized as highly efficient soft colloidal emulsifiers for stabilizing water-in-oil-water (W/O/W) Pickering emulsions due to the excellent interfacial activity. Meanwhile, the assembled particle structures could be modulated by adjusting the oil-water ratio, resulting from the tunable aggregation behavior of supra-amphiphilic macromolecules. Additionally, the interfacial adsorption films could be partially destroyed/reconstructed upon ultraviolet/visible irradiation due to the stimuli-altering balance of amphiphilicity of Alg-β-CD/AzoC12 polymers, further constructing the stimulus-responsive Pickering emulsions. Therefore, the supramolecular interfacial self-assembly-mediated approach not only technologically advances the continued development of creative templates to construct multifunctional soft materials with anisotropic structures but also serves as a creative bridge between supramolecular host-guest chemistry, colloidal interface science, and soft material technology.

Comparison of Nanomaterials for Enhanced Oil Recovery in Tight Sandstone Reservoir

With dwindling conventional oil resources, the development of high-performance oil-displacing agents to exploit unconventional oil and gas resources has become a research focus, and new technical ideas have been proposed for petroleum engineering with the advancement of nanomaterials and technology. This study characterized the microscopic pore throat structure of the unconventional tight sandstone reservoir of Ordos Basin in China comprehensively by using high-resolution scanning electron microscopy, image panoramic mosaic technology, mineral quantitative scanning system, and 3D image of pore. A new nanofluid with diphenyl ether surfactants as shell and C10–C14 straight-chain hydrocarbon compounds as kernel was prepared according to the features of tight sandstone reservoirs. The basic physical properties of the nanofluid were evaluated and compared with those of three other generic oil-displacing agents to understand the oil-displacement effect and mechanism. Results show that this nanofluid remains relatively stable and dispersible with aging and its average particle size matches well with the pore throat size of the target reservoir, which increases the sweep volume effectively. Additionally, the change from oil-wet to water-wet can exert capillary imbibition. And the oil-water interfacial tension can be greatly reduced to the level of 10–2 mN/m because of nanofluid’s excellent interfacial activity, which improves the efficiency of oil washing in nano-scale pore throats. Finally, the core imbibition experiment further demonstrated the superiority of the nanofluid. Using the nanofluid in optimal concentration with cores of approximately 0.1 mD can achieve a recovery rate of 37.5%, which is higher than generic oil-displacing agents by up to 9%. This study demonstrates that the excellent performance of nanofluid in enhancing oil recovery and provides a reference for the development of unconventional reservoirs, which are difficult to function with generic agents.

Janus Micelles by Crystallization-Driven Self-Assembly of an Amphiphilic, Double-Crystalline Triblock Terpolymer.

Surface-compartmentalized micellar nanostructures (Janus and patchy micelles) have gained increasing interest due to their unique properties opening highly relevant applications, e.g., as efficient particulate surfactants, compatibilizers in polymer blends, or templates for catalytically active nanoparticles. We present a facile method for the production of worm-like Janus micelles based on crystallization-driven self-assembly of a double-crystalline triblock terpolymer with a crystallizable polyethylene middle block and two highly incompatible corona blocks, polystyrene and poly(ethylene oxide). This approach enables the production of amphiphilic Janus micelles with excellent interfacial activity by a comparably simple heating and cooling protocol directly in solution.

Ionic liquid-functionalized amphiphilic Janus nanosheets afford highly accessible interface for asymmetric catalysis in water

High oil/water interfacial area together with accessible interfaces for regents is the key to achieving efficient asymmetric catalysis in water. Herein, by taking advantage of the excellent interfacial activity of Janus nanosheets (JNS), as well as the unique compatibility of imidazolium ionic liquid (IL), we developed a series of IL-functionalized amphiphilic Janus mesosilica nanosheets which afford highly accessible reaction interfaces for highly enantioselective sulfoxidation in water. The JNS-typed chiral salen TiIV catalysts were prepared by selectively decorating hydrophobic chiral salen TiIV complex on one side of Janus mesosilica nanosheets through the imidazolium-based IL linker. Benefiting from the two-dimensional porous Janus structure, as well as the compatible IL linker, the IL-tagged JNS catalysts afforded high oil/water interfacial areas and highly accessible reaction interface for sulfides and H2O2, significantly accelerating asymmetric sulfoxidation in water using H2O2 as an oxidant. In addition, they can be facilely recovered for stable reuse by simple centrifugation.

Preparation and properties of amphiphilic hydrophobically associative polymer/ montmorillonite nanocomposites.

In this research, a novel amphiphilic hydrophobically associative polymer nanocomposite (ADOS/OMMT) was prepared using acrylamide (AM), sodium 4-vinylbenzenesulfonate (SSS), N, N′-dimethyl octadeyl allyl ammonium bromide (DOAAB) and organo-modified montmorillonite (OMMT) through in situ polymerization. Both X-ray diffraction patterns and transmission electron microscopy images verified the dispersion morphology of OMMT in the copolymer matrix. Then, the effect of the introduction of OMMT layers on the copolymer properties was studied by comparing with pure copolymer AM/SSS/DOAAB (ADOS). The thermal degradation results demonstrated that the thermal stability of the ADOS/OMMT were better than pure copolymer ADOS. During the solution properties tests, ADOS/OMMT nanocomposite was superior to ADOS in viscosifying ability, temperature resistance, salt tolerance, shear resistance and viscoelasticity, which was because OMMT contributed to enhance the hydrophobic association structure formed between polymer molecules. Additionally, the ADOS/OMMT nanocomposite exhibited more excellent interfacial activity and crude oil emulsifiability in comparison to pure copolymer ADOS. These performances indicated ADOS/OMMT nanocomposite had good application prospects in tertiary recovery.

CO2/N2-responsive oil-in-water emulsions using a novel switchable surfactant

HypothesisRecently, switchable or stimuli-responsive emulsions have attracted much research interest in many industrial fields. In this work, a novel CO2/N2-responsive surfactant was designed and developed to facilitate the formation of switchable oil-in-water (O/W) emulsions with fast switching characteristics between a stable emulsion and separate phases upon alternatively bubbling CO2 and N2. ExperimentsThe novel CO2/N2-responsive surfactant was facilely prepared by mixing an anionic fatty acid (oleic acid) and a cationic amine (1,3-Bis (aminopropyl) tetramethyldisiloxane) at a 1:1 molecular ratio, which was assembled based on electrostatic interactions. The structure and properties of the novel CO2/N2-responsive switchable surfactant were investigated by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) spectroscopy, and interfacial tensions. FindingsThe developed surfactant shows an excellent interfacial activity at the oil/water interface, which can significantly reduce the dosage of the switchable surfactant compared with previous CO2/N2-responsive surfactants. The dynamic interfacial tension of n-decane and aqueous phase decreased from 45 mN m−1 to 5 mN m−1 within 100 s with the addition of 0.2 mM surfactant. In this work, a low concentration of the novel switchable surfactant (e.g., 20.0 mM) can realize reversible emulsification and demulsification in an emulsion system as compared with the high dosage (e.g., ~150 mM) in previous reports, which will bring huge economic benefits in industrial applications in the future. Moreover, this work expands the family of ion-pair surfactants to small amino-functionalized molecules beyond Jeffamine D-230, which promotes the development of simple and switchable ion-pair surfactant. It is found that the O/W emulsions stabilized by the switchable surfactant show excellent stability, which can be stored for over 60 days at room temperature without any obvious change. Interestingly, the stable O/W emulsion is completely demulsified upon bubbling CO2 for 30 s and can be easily re-emulsified to the initial state after purging N2 at 60 °C within 10 min, which demonstrates a rapid and highly efficient switching behavior. The reversible emulsification and demulsification process is ascribed to the reversible assembly and disassembly of the switchable surfactant, which is induced by the removal and purge of CO2.