Stability Of Microemulsions Research Articles

Unraveling the Phase Behavior and Stability of Surfactant-Free Microemulsions: From Molecular Interactions to Macroscopic Properties.

Surfactant-free microemulsions (SFMEs), formed in mixed ternary systems such as water/ethanol/oil, have garnered substantial interest due to their unique properties and broad applications in areas such as enzyme-catalyzed reactions and nanoparticle synthesis. In this work, we conducted an in-depth investigation of the spontaneous nucleation and stabilization mechanisms of SFMEs, employing experimental techniques, molecular dynamics (MD) simulations, and Flory-Huggins (F-H) theory. The formation of multiscale nanostructures (characteristic scales of ∼1 and ∼100 nm) and their interfacial charging characteristics in SFMEs have been revealed experimentally. MD simulations investigated the structure and stability on the microscopic scale, enhancing our understanding of molecular interactions within these microemulsions. Our theoretical analysis revealed that the stability of mesoscopic nanodroplets within SFMEs hinges on a delicate balance between mixing entropy and internal energy. Equilibrium between these energies results in stable nanodroplet solutions, showcasing a delicate balance that can be manipulated by adjusting the volume fractions of the components and their interaction parameters. This research not only advances the theoretical understanding of SFMEs but also highlights their potential in industrial applications, emphasizing the importance of integrating theoretical and experimental approaches to develop functional nanostructured materials.

Thermodynamic stability of a spin microemulsion in Rashba spin-orbit-coupled bosons

Thermodynamic stability of a spin microemulsion in Rashba spin-orbit-coupled bosons

Structure and Potential Application of Surfactant-Free Microemulsion Consisting of Heptanol, Ethanol and Water

Microemulsions, which are thermodynamically stable and isotropic mixtures of water, oil, and surfactants, attract significant research interest due to their unique physicochemical properties and diverse industrial applications. Traditional surfactant-based microemulsions (SBMEs) stabilize the interface between two typically immiscible liquids, forming various microstructures such as oil-in-water (O/W) droplets, water-in-oil (W/O) droplets, and bicontinuous phases. However, the use of surfactants poses environmental concerns, cost implications, and potential toxicity. Consequently, there is increasing interest in developing surfactant-free microemulsions (SFMEs) that offer similar benefits without the drawbacks associated with surfactants. In this study, we explore the formation and characteristics of a new surfactant-free microemulsion in a ternary system comprising water, ethanol, and heptanol. Advanced techniques are employed to characterize the microstructures and stability of surfactant-free microemulsions. These include electrical conductivity measurements, surface tension analysis, dynamic light scattering (DLS), and Fourier transform infrared spectroscopy (FTIR). These methods have been extensively used in previous research on surfactant-free microemulsions (SFMEs) to reveal the properties and interactions within microemulsion systems. The area of interest is identified using these techniques, where silica nanoparticles are subsequently synthesized and then visualized using transmission electron microscopy (TEM).

Oil-in-water microemulsion of Arthrospira platensis carotenoid as antiphotooxidation in vitamin C beverages

Arthrospira platensis is a blue-green microalgae that has carotenoid as the main pigments, with the largest content being beta-carotene. Carotenoids are a type of pigment that is water insoluble, unstable, and has a limited bioavailability. One of the efforts to improve its solubility and stability, especially with regard to its anti-photooxidation capabilities, is to make it into a microemulsion. This study aimed to develop the most stable oil-in-water (O/W) microemulsion containing carotenoids from A. platensis for use as an antiphotooxidation agent in vitamin C beverages. Microemulsions consist of three distinct phases: oil, water and surfactant. The oil phase consisted of virgin coconut oil (VCO) or palm oil, with 7.5% and 15% and the aqueous phase was distilled water at a concentration of 65% or 80%. The surfactant used a combination of Tween 80, Tween 20, and Span 80 with a final hydrophilic-lipophilic balance or HLB value of 14.5. All microemulsion formulations were incubated for 24 hrs before being tested for stability by centrifugation at 3000 rpm for 30 mins, heating at 105oC for 5 hrs, and storage for 2 and 4 weeks. The resulting turbidity index was used to test the microemulsion's stability. The most stable microemulsion was chosen as a delivery system for carotenoid compounds. The carotenoid microemulsion was also tested by centrifugation, heating, and stability at different pH (6.5 and 4.2) and in varied ratios (1:1, 1:9 and 1:99). The results revealed that the concentration of oil and water phases in the microemulsion formulation influenced the microemulsion's stability. The best formulation obtained was a microemulsion with 7.5% of virgin coconut oil, 80% of water concentration, and surfactant with a ratio of 92:5.5:2.5 (Tween 80: Span 80:Tween 20). The most stable carotenoid microemulsion was a microemulsion with 100 ppm of carotenoid added. The carotenoid microemulsion was able to inhibit photooxidation at 4000 lux for 4 hrs. The vitamin C beverage model added with 6 ppm carotenoid microemulsion was able to inhibit photooxidation compared to the control and 12 ppm, for up to 6 hrs and there was a significant decrease in vitamin C and antioxidants after 24 hrs of photooxidation. A. platensis carotenoid microemulsion with a concentration of 6 ppm could inhibit photooxidation on vitamin C beverages for up to 6 hrs.

An effective strategy to construct pH-responsive microemulsion for cobalt recovery and its responsive mechanisms

Microemulsions for heavy metal separation show advantages of fast separation rate, high separation efficiency and extraction capacity. However, it remains challenging in destabilizing microemulsions for back-extraction due to their thermodynamic stability. This study describes an effective strategy to construct pH-responsive microemulsion by adding N,N-dimethylethanolamine (DMEA) during back-extraction to avoid the negative impact of responsive materials on the extraction, meanwhile the back-extraction can be realized through a mild pH stimulus compared to traditional strong acid demulsifier. Cetyltrimethylammonium bromide (CTAB)-stabilized microemulsion was formulated and optimized for the selective Co(II) extraction reaching 95.4 %, while extraction efficiency of Ni(II) kept low at 10.5 %. The back-extraction efficiency of Co(II) reached 99.53 %. The responsive mechanism was studied by measuring the dynamic interfacial tension and interfacial dilatational rheology of CTAB solution in heptane under the effects of NaCl, DMEA and pH. By pH stimulus, DMEA protonated and increased the ionic strength, consequently inducing a “salting-out” effect and deactivating CTAB at oil-water interface, ultimately destabilizing the microemulsion. This study proposes a new approach for constructing responsive microemulsions for recovering heavy metals and also provides useful information on its responsive mechanisms by establishing a relationship between interfacial property and macroscopic stability of microemulsions.

Water-in-oil microemulsions with greener oil solvents as sustainable nanoreactors of biopolymer nanoparticles

Microemulsions have been widely used in multidisciplinary fields, yet reverse water-in-oil microemulsions are traditionally dispersed in petroleum-based oil solvents. For greener approaches, it should be also feasible to use less toxic, bio-based hydrocarbon solvents as continuous oil phase. Herein, reverse microemulsions in different alkanes, middle-chain alkanols, middle-chain esters or combinations of nonpolar solvent with alkanol are compared, using Aerosol-OT as common surfactant. As model of bio-based solvents, ethyl caprylate, isoamyl acetate and isoamyl alcohol are proposed as a more sustainable approach of oil solvents. Various characterization techniques were used to compare the properties and stability of reverse microemulsions for the different oil phase compositions, ranging from ternary phase diagrams to conductometry and turbidity titrations, micro-Differential Scanning Calorimetry and cryo-Scanning Electron Microscopy. As sustainable application, these microemulsions in bio-based solvents were proved suitable as template phase for the synthesis of cross-linked chitosan nanoparticles. The sizes of the resulting biopolymer nanoparticles were characterized by Dynamic Light Scattering and Atomic Force Microscopy, so that the effect of different crosslinkers and different the oil phase compositions was also compared. Thus, the use bio-based alkyl esters can provide similar microemulsion properties as the conventional alkanes, especially when using a combination of nonpolar solvents with alkanols.

Microemulsion Characteristics of Oil-in-Water with Surfactants as α-tocopherol Carriers

Microemulsions are relatively stable carrier agents for bioactive components. This study aimed to determine the characteristics of oil-in-water (O/W) microemulsions as carriers of α-tocopherol compounds in variations of α-tocopherol concentration, pH, and dilution. The O/W microemulsion was made from a mixture of surfactants (Tween 80, Tween 20, and Span 80) with virgin coconut oil (VCO) in a ratio of 85:15 with a total volume of 5 mL added with 10 mL of distilled water. The research used a randomized block design (RBD). The data were analyzed using ANOVA and continued with Tukey's test and regression analysis. Treatments in microemulsion were the addition of α-tocopherol with concentrations of: 0.25, 1.50, 1.75 and 2.0%. Observations were made on the turbidity index values, appearance, droplet diameter, and microemulsion stability. In addition, observations were made on the stability of the microemulsion at variations of pH (4.5, 5.5, 6.5), and dilution (10, 50, and 100 times). The results showed that the microemulsion was able to carry α-tocopherol compounds up to a concentration of 2% with a turbidity value reaching 0.1036 ± 0.0033% with a transparent appearance. A mixture of three surfactants (Tween 80, Tween 20 and Span 80) has the ability to increase droplet stability. The α-tocopherol microemulsion had a droplet diameter below 30 nm and stayed stable against the effects of centrifugation at pH 4.5 with dilutions up to 50 times and remained stable upto pH 6.5 with dilutions between 50 – 100 times.

The behavior of surfactant microemulsion in clay-hosted nanopores

The utilization of microemulsions to boost well productivity is gaining traction, particularly in unconventional shale wells during fracturing. However, the subsequent behavior and stability of microemulsions remain less clear, especially in clay-hosted nanopores where clay minerals exhibit unbalanced surface charges. This study employs the molecular dynamics (MD) approach to characterize the behavior and stability of microemulsion droplets through clay-hosted nanopores with different surface chemistries and salinities in shales, under typical reservoir pressures and temperatures. Our findings reveal that in the bulk, microemulsion droplets remain stable across all salinities. Yet, depending on the surface chemistry (charge distribution) in clays, the stability of microemulsion droplets becomes contingent on salinity. When clay surfaces are charge-balanced or have a moderate imbalance, microemulsion droplets remain stable. However, with a strong charge imbalance, induced local electric fields in the slit pore affect the fluids, leading to the essential role of both the electric field and clay surface in breaking the microemulsion droplet. Increasing salinity results in the formation of an electrical double layer, diminishing the strength of the electric field, and preserving the stability of microemulsion droplets. This modeling-based work enhances our comprehension of salinity variations' impact on microemulsions in charged clay hosted nanopores. Notably, this is the inaugural study combining and assessing microemulsion sensitivity to salinity and pore surface chemistry, thereby broadening possibilities for the effective delivery of EOR agents to shales.

Thermal stability of water-in-oil microemulsions containing solubilized nutritional protein gelatin

To develop new food and pharma technologies, various combinations of encapsulation and delivery of biological macromolecules are used. Proteins, polysaccharides, fats and lipids must be conveyed inside living organism, protecting them during the stages of storage and preparation from exposure of aggressive external environment. Some of the most common food protein compositions are various gels and emulsions. In the present study, we focused our attention on the influence of protein molecules on the properties and dynamical stability of water-inoil microemulsion. Microemulsions, the oil dispersion of surfactant-based reverse micelles, each carrying nanosized water core with embedded protein. We studied the result of protein encapsulation in the water core of surfactant reverse micelles, namely, the fish and mammalian gelatin. The method of electric conductivity was explored to detect the properties of reverse micelles as containers for food proteins. We have shown that a rather high protein content does not destroy microemulsion structure, which retain reverse micelles, though the properties of the system undergo definite alterations, in particular, it substantively lost thermal stability accelerating exchange processes between reverse micelles at lower temperatures which have to be taken into account in nutritional and pharmacy objectives.

Laboratory Study of Analysis of the Effect of ABS Surfactant Injection on Increasing Oil Recovery

The decline in oil recovery in oil and gas fields is a problem that must be faced now and in the future along with the increasing need for petroleum energy. Increasing oil recovery reserves requires an advanced method, namely Enhanced Oil Recovery (EOR). Surfactants are one of the enhanced oil recovery (EOR) methods to increase oil recovery. This laboratory research will use a surfactant solution, namely ABS Surfactant (Alkyl Benzene Sulfonate). There are five concentrations for each surfactant, namely 0.3; 0.5; 0.75; 0.9; and 1% with the same salinity of 7,000 ppm. In this study, ABS surfactant was used because the surfactant has the characteristic of being able to reduce interfacial tension. This research carried out a phase behavior test to determine the stability of the emulsion with a measurement time of 7 days at a temperature of 80 °C. Making an ABS surfactant solution, 70% ABS fluid is available where the surfactant raw material will be mixed with brine with a salinity of 7,000 ppm. There are several stages carried out, namely density test, phase behavior, interfacial tension, and core flooding. After making a sample of the ABS surfactant solution, the second step was to carry out a density test using a DMA-4100 densitometer to determine the density of the ABS surfactant solution at temperatures of 30 °C and 80 °C. The third is a phase behavior test where the surfactant solution will be mixed with oil and then placed in an oven at a temperature of 80 °C for 336 hours to obtain emulsion results that are close to the midpoint so that the stability of the emulsion is more optimal. The fourth is to determine the IFT value with a surfactant sample that has the highest volume of microemulsion stability. Finally, the core flooding test is to determine how much oil is recovered from the sandstone when surfactant injection is carried out. In the IFT results, the ABS surfactant solution was able to reduce the interfacial tension well between oil and formation water in the reservoir, where the interfacial tension value was 0.0055654 dyne/cm. The results of core flooding with ABS surfactant with a concentration of 0.9% salinity of 7,000 ppm obtained a recovery factor of 14.545%.

Stable bulk nanobubbles can be regarded as gaseous analogues of microemulsions

In our previous work [2022 Phys. Chem. Chem. Phys. 24 9685], we used molecular dynamics simulations to show that bulk nanobubbles can be stabilized by forming a compressed amphiphile monolayer at bubble interfaces. This observation closely matches the origin of stability of microemulsions and inspired us to propose here that, in certain cases, stable bulk nanobubbles can be regarded as gaseous analogues of microemulsions: the nanobubble phase and the bubble-containing solution phase coexist with the external gas phase. This three-phase coexistence is then validated by molecular dynamics simulations. The stability mechanism for bulk nanobubbles is thus given: the formation of a compressed amphiphilic monolayer because of microbubble shrinking leads to a vanishing surface tension, and consequently the curvature energy of the monolayer dominates the thermodynamic stability of bulk nanobubbles. With the monolayer model, we further interpret several strange behaviors of bulk nanobubbles: gas supersaturation is not a prerequisite for nanobubble stability because of the vanishing surface tension, and the typical nanobubble size of 100 nm can be explained through the small bending constant of the monolayer. Finally, through analyzing the compressed amphiphile monolayer model we propose that bulk nanobubbles can exist ubiquitously in aqueous solutions.

Revealing the microscopic formation mechanism and stability characteristics of anionic surfactant microemulsions using coarse-grained simulations

Microemulsion is thermodynamically stable dispersion system formed by emulsifiers such as surfactants adsorbed at the oil-water interface. However, the evolution mechanism of surfactant-stabilized microemulsions and its stability are not adequately understood. Motivated by these issues, the underlying formation mechanism and the complex interplay on the microemulsion stability were systematically investigated by dissipative particle dynamics simulations. Coarse-grained models of oil/water/surfactants were developed to demonstrate a clear Ostwald ripening mechanism for W/O microemulsion, whereas a collisional fusion mechanism for O/W microemulsion. Mutual transformation between O/W and W/O microemulsions was dominated by the change of interfacial water/oil area. As the surfactant concentration increased, smaller microemulsion formed with a higher stability. Compared to sodium lauryl sulfonate, sodium dodecylbenzene sulfonate with benzene structure could form a thicker interfacial film, thereby improving the microemulsion stability. Internal olefin sulfonate with a branched structure was able to form an interfacial film with greater strength, enduring a higher shear rate of 0.033/ps. Furthermore, longer molecular chains of surfactant could result in a stronger steric effect, leading to a higher salinity tolerance of microemulsion with aHH is 17. The obtained results are expected to provide a solid theoretical foundation for the rational design of efficient microemulsions and pave the way for the applications such as oil recovery, pollution control, and dispersion of drugs.

Formulation and stability study of vitamin E microemulsion with green surfactant

To satisfy the urge for green life, the preparation of various microemulsions using green surfactants has become a new research hotspot. To improve the utilization of vitamin E (VE) oil, the O/W microemulsions of VE were successfully prepared by a pseudo-ternary phase diagram method with three green surfactants. All of the microemulsions are transparent and uniform-looking. The average size of spheres is in the range of 30–75 nm. The stability of microemulsions was determined by storage, temperature and centrifugation. They remained stable for up to 4 months. The antioxidant capacity of microemulsions was 2.99 times higher than that of ordinary VE, and they were less susceptible to oxidative inactivation. This work has successfully constructed food-grade microemulsions with high VE content and free of other oil phases by simple stirring using a completely green surfactant and cosurfactant, which is one more step towards the better application of VE products in food, medicine and industrial fields.

Fingerprinting pattern of orange essential oils in surfactant-free microemulsion by 3D fluorescence spectroscopy

The effect caused by surfactant-free microemulsion (SFME) systems in orange essential oil analysis was evaluated by 3D fluorescence spectroscopy. The SFME formation region was studied at different water:EO proportions (1:4, 1:2, 1:1, 2:1, 4:1 w/w) in the presence of propanol and octanol (10:3 w/w). Conductometric titrations indicated micellar aggregates containing EO (oil-in-water microemulsion) for the 4:1 proportion (droplets of hydrodynamic radius of 95.7 ± 5.3 nm). In such conditions, fluorescence increased allowing the use of 3D fluorescence spectroscopy to obtain spectroscopic fingerprint pattern that was used aiming discriminant analysis, considering nine EO Brazilian brands, along with unfold principal component analysis (UPCA). Cumulative variance of 96.7 % was obtained for the first three principal components and score plots showed distinct location for each group. Preliminary study showed the capability of these systems in evaluating storage conditions, and adulteration. The impact of storage conditions was made over 21 days exposed to light with results showing large spectral differences compared to a sample stored in amber flask at 22 °C. Adulteration of EOs by canola and mineral oil fortification was detected at different levels (1, 5, 10 and 20 %, in mass proportion) and, in addition to the spectral differences, a change in microemulsion stability was observed.

Emulsion electrospinning of zein nanofibers with carotenoid microemulsion: Optimization, characterization and fortification

In this study, carotenoid microemulsion was encapsulated in zein nanofibers via emulsion electrospinning. Optimization study was applied to determine optimum parameters by response surface methodology. The voltage, flow rate and distance as optimum conditions were determined as 23 kV, 1.7 mL/h and 12.75 cm, respectively. Lycopene, β-carotene, encapsulation efficiency, encapsulation yield and zeta potential of zein nanofibers in optimum conditions were estimated as 4.054 mg/kg, 0.649 mg/kg, 77.78%, 41.76% and −29.73 mV, respectively. The addition of microemulsion affected nanofibers diameter and morphologies. Diffusion coefficient of zein nanofibers decreased with addition of microemulsion under optimum conditions. The electrospinning improved thermal stability of microemulsion. The carotenoid microemulsion could be entrapped into the zein fibers according to ATR–FTIR spectrum. Model foods were fortificated with zein nanofibers. The addition of nanofibers changed color of the foods during the storage. Carotenoid compounds were more stable in nanofibers followed by olive oil, milk and water.

The formation and temperature stability of microemulsion emulsified by polyoxyethylene ether surfactant

The effect of polyoxyethylene chain length on the formation and temperature stability of W/O microemulsion emulsified by polyoxyethylene ether surfactant is investigated by dissipative particle dynamics simulation (DPD) on the mesoscopic level. The results show that W/O microemulsions can be formed by three polyoxyethylene chain length ether nonionic surfactants with decreasing the water-oil ratio equal to increasing the oil phase content. However, W/O microemulsion is most easily formed by diethylene glycol monododecyl ether (H1T2) with the smallest oxyethylene base.The results of temperature stability show that W/O microemulsion emulsified by H1T2 has better stability resistant to high or low temperature. In addition, the interfacial tension of the W/O microemulsion system is the lowest, the end-to-end distance of the surfactant molecule is smallest, and the molecular chain is the most curved at the water-oil interface. The theoretical simulation results can guide the formation of the W/O microemulsion induced by polyoxyethylene ether nonionic surfactant, and provide the guidance for its practical application.

Redox-responsive microemulsion: Fabrication and application to curcumin encapsulation

HypothesisStimulus-responsive microemulsions have aroused significant attention because of their versatile and reversible switchability between stable and unstable states. However, most stimuli-responsive microemulsions are based on stimuli-responsive surfactants. We posit that the change in the hydrophilicity of a selenium-containing alcohol triggered by a mild redox reaction could also influence the stability of microemulsions and provide a new nanoplatform for the delivery of bioactive substances. ExperimentsA selenium-containing diol (3,3′-selenobis(propan-1-ol), PSeP) was designed and used as a co-surfactant in a microemulsion with ethoxylated hydrogenated castor oil (HCO40), diethylene glycol monohexyl ether (DGME), 2-n-octyl-1-dodecanol (ODD) and water. The redox-induced transition in PSeP was characterized by 1H NMR, 77Se NMR, and MS. The redox-responsiveness of the ODD/HCO40/DGME/PSeP/water microemulsion was investigated through determination of a pseudo-ternary phase diagram, analysis by dynamic light scattering, and electrical conductivity, and its encapsulation performance was evaluated by determination of the solubility, stability, antioxidant activity, and skin penetrability of encapsulated curcumin. FindingsThe redox conversion of PSeP enabled efficient switching of ODD/HCO40/DGME/PSeP/water microemulsions. Addition of oxidant (H2O2), oxidized PSeP into more hydrophilic PSeP-Ox (selenoxide), disrupting the emulsifying capacity of the combination of HCO40/DGME/PSeP, markedly reducing the monophasic microemulsion region in the phase diagram, and inducing phase separation in some formulations. Addition of reductant (N2H4·H2O), reduced PSeP-Ox and restored the emulsifying capacity of the combination of HCO40/DGME/PSeP. In addition, PSeP-based microemulsions can significantly enhance the solubility in oil (by 23 times), stability, antioxidant capacity (DPPH∙ radical scavenging by 91.74 %), and skin penetrability of curcumin, showing clear potential for encapsulation and delivery of curcumin and other bioactive substances.

An experimental investigation on the impact of divalent ions on the emulsification of oil: Comparison of biodegradable (green) and petroleum-based surfactants

Emulsification of oil with surfactants often yields in complex colloidal systems which require understanding their physicochemical properties prior to their use in industry. This study aims to investigate the effects of divalent ions (calcium and magnesium) on the emulsification performance of biodegradable (green) surfactants of Triton™ CG-110 (alkyl polyglycoside, APG) and GreenZyme (GZ) at two temperature conditions (25 °C and 70 °C). For this purpose, the phase behaviour, interfacial tension (IFT), stability, droplet size distribution and rheological properties of APG and GZ microemulsion were evaluated. The outcomes were then compared with the emulsification performance of petroleum-based (synthetic) surfactants of alpha-olefin sulfonate (AOS) and cetyltrimethylammonium bromide (CTAB). Furthermore, the impacts of alkalis (ethanolamine and sodium carbonate) on microemulsions and the demulsification performance of a zwitterionic demulsifier (cocobetaine) were explored. The results show that only APG and CTAB could produce water in oil (W/O) microemulsions in the presence of divalent ions. The stability of APG and CTAB microemulsions was affected by divalent ions since the water segregation rate (WSR) index of these microemulsions went up from ≈21% to ≈ 85% as salinity increased up to 15 wt%. Also, the average droplet size of these microemulsions went up from 50-64 nm to 220–255 nm as salinity increased to 9 wt%. This is because the negative charge density on the microemulsion droplet surface decreases as the salinity increases, thus the electrostatic repulsive force between the droplets becomes weaker. In addition, APG and CTAB microemulsions showed a shear thinning behaviour, and their viscosity value increased with the increase in salinity. It is speculated that the presence of divalent ions generates more friction between the molecules, which causes an increase in the viscosity of the microemulsions.

The formation and stability of microemulsions formed with organic solvent as inner/outer phases: Insight from DPD simulation

Organic solvents are selected as the inner/outer phases to construct the microemulsion systems can open new areas of application in providing a reaction medium for various organic conversions. O/W and reverse W/O microemulsions are prepared, using four different organic solvents of Benzene, Cyclohexane, Octane and Dodecane and nonionic surfactant Dodecylhexaglycol (C12E6) as a stabilizer by using Dissipative particle dynamics (DPD) simulation method. The oil–water ratio is applied to control the topology of the microemulsions and more importantly achieve the transformation of O/W and reverse W/O microemulsions. For cyclic hydrocarbons, Cyclohexane needs the same ratio to form O/W microemulsions and reverse W/O microemulsions with Benzene though possessing the special π chemical bond. However, the liner hydrocarbon with a short molecular chain of Octane is conducive to form O/W microemulsions and the longer chain of Dodecane is easier to create reverse W/O microemulsions. The interfacial tension and end-to-end distance values are lowest when O/W and reverse W/O microemulsions are formed in the system. The temperature-induced stability results show that O/W microemulsions have the same stability for four organic solvents, but Cyclohexane and Octane present superior strength than Benzene and Dodecane for reverse W/O microemulsions. In addition, the more substantial hydrophobic effect of Cyclohexane and Dodecane promotes better salt-induced stability for O/W microemulsions, interestingly, reverse W/O microemulsions present the same stability for four systems. Our findings are instructive in providing the physical understanding necessary for future progress in research and applications of microemulsions, especially for organic solvents as the oil phase in the field of microreactors.

Integrated Thermoelectric Design Inspired by Ionic Liquid Microemulsion-Based Gel with Regulatable Dual-Temperature Responsiveness

The concept and principles of chromatic engineering of electrolytes have demonstrated charming prospects for constructing pluralistic electrochromic devices. Here, we develop a synthetic design bearing thermochromic and electrochromic behaviors based on the ionic liquid (IL) microemulsion-based gel, driven by the intrinsic thermodynamic stability of microemulsion and ionic conductivity of IL. The prepared gel can tune light-scattering behaviors as the droplet expanded or aggregated when the temperature is out of its thermodynamically stable temperature range. Not only that, oil-phase IL ([EMIM]TFSI) as well as introduced LiCl and LiTFSI endows it with satisfactory ionic conductivity, making it able to be utilized as a free-standing electrolyte layer for the electrochromic smart window. Therefore, the fabricated smart window based on this gel and WO3 electrochromic layer successfully realizes dual-stimuli responsiveness for both temperature and electric field, possessing energy-saving combined with privacy protection function. In addition, the component compatibility of microemulsion allows the harmonious introduction of hydrophilic antifreeze moisturizer ethylene glycol (EG) and hydrophobic ultraviolet absorber 2-hydroxy-4-(octyloxy)benzophenone (2H4MBP), which further promotes the multifunctional integration of a smart window for the strengthened safety factor, anti-freezing, anti-drying, and anti-UV capabilities. Finally, we extend the application of the IL microemulsion-based gel to an ionic writing plate based on the same electrochromic mechanism. In brief, this innovative preparation method paves the way for multifunctional electrochromic devices.