Emulsion Type Research Articles

Encapsulation of antioxidants with colloidal lipid particles for enhancing the photooxidation stability of phytosterol in Pickering emulsions

In order to prevent the photooxidation of phytosterols, a new type of Pickering emulsion was developed by regulating the oriented distribution of antioxidants in colloidal lipid particles (CLPs) at the oil-water interface. High-melting-point and low-melting-point lipids were tested to modulate their protective effect against phytosterols photooxidation. Results showed that CLPs could stabilize Pickering emulsion and encapsulate antioxidants, providing a dual functional delivery system for phytosterols protection. The Pickering emulsion formed had a particle size of around 350–820 nm, and the crystallization and melting temperatures of tripalmitin particles were approximately 32 °C and 63.8 °C, respectively. The addition of tributyrin or tricaprylin reduced the crystallization and melting temperatures of Pal CLPs and improved the photooxidation emulsion stability. The prepared Pickering emulsion remained stable for a maximum of 12 days under accelerated light-induced oxidation. Among all formulations, the emulsion primarily composed of tripalmitin CLPs, with added tributyrin and resveratrol, exhibited the highest photooxidation stability.

Metathetic degradation of waste vulcanized emulsion type butadiene-based rubber

Metathetic degradation has been recognized as promising strategy for the treatment of waste vulcanized rubbers as a Waste-to-Resources approach, not only eliminating the pollution but also recycling as resources. However, it was mainly used for the treatment of the waste vulcanized natural rubber, which contains plentiful cis-1,4- structure. Despite of a much higher consumption of the emulsion type butadiene-based rubbers than natural rubber, there was no report on the metathetic degradation of the waste vulcanized emulsion type butadiene-based rubbers due to their less cis-1,4- unit, although the metathetic functionalization of the nonvulcanized emulsion type butadiene-based rubbers have been well reported. Here, the metathetic degradation of waste vulcanized emulsion type butadiene-based rubber was explored with nitrile-butadiene rubber (NBR) glove as a model. Different from the metathetic degradation of waste vulcanized natural rubber via only cross metathesis between cis-1,4-structure and the chain transfer agent (CTA), the ring closing metathesis between the adjacent cis-1,4-structure and 1,2-structure also occurred in the metathetic degradation of waste vulcanized NBR. It is expected to open the door for the Waste-to-Resources approach of all waste vulcanized emulsion type diene-based rubbers.

Comparison of two formulations of intravenous lipid emulsions in pediatric intestinal failure.

The effect of different types of lipid emulsion may guide therapy of patients with intestinal failure (IF) to limit morbidity such as intestinal failure-associated liver disease (IFALD). A retrospective chart review of pediatric patients with IF who received soybean oil lipid emulsion (SL) or mixed oil lipid emulsion (ML) was performed. Data over 1 year were collected. Forty-five patients received SL and 34 received ML. There were no differences in the incidence (82 versus 74%, P = 0.35) or resolution (86 versus 92%, P = 0.5) of IFALD between the cohorts. The median dose of ML was higher compared to SL (2 versus 1g/kg/day, P < 0.001). If resolved, IFALD resolved rapidly in the ML cohort compared to the SL cohort (67 versus 37days, P = 0.01). Weight gain was higher in the ML compared to the SL cohort at resolution of IFALD or 1 year from diagnosis of IF (P = 0.009). The administration of ML did not alter the incidence or resolution of IFALD compared to SL in pediatric IF. There was rapid resolution of IFALD and enhanced weight gain in the ML cohort compared to SL in pediatric IF.

Influence of physico-chemical properties of two lipoxin emulsion-loaded hydrogels on pre-polarized macrophages: a comparative analysis.

Inflammation, a crucial defense mechanism, must be rigorously regulated to prevent the onset of chronic inflammation and subsequent tissue damage. Specialized pro resolving mediators (SPMs) such as lipoxin A4 (LXA4) have demonstrated their ability to facilitate the resolution of inflammation by orchestrating a transition of M1 pro-inflammatory macrophages towards an anti-inflammatory M2 phenotype. However, the hydrophobic and chemically labile nature of LXA4 necessitates the development of a delivery system capable of preserving its integrity for clinical applications. In this study, two types of emulsion were formulated using different homogenization processes:mechanical overhead stirrer (MEB for blank Emulsion and MELX for LXA4 loaded-Emulsion) or Luer-lock syringes (SEB for blank Emulsion and SELX for LXA4 loaded-Emulsion)). Following characterization, including size and droplet morphology assessment by microscopy, the encapsulation efficiency (EE) was determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). To exert control over LXA4 release, these emulsions were embedded within silanized hyaluronic acid hydrogels. A comprehensive evaluation, encompassing gel time, swelling, and degradation profiles under acidic, basic, and neutral conditions, preceded the assessment of LXA4 cumulative release using LC-MS/MS. Physicochemical results indicate that H-MELX (Mechanical overhead stirrer LXA4 Emulsion loaded-Hydrogel) exhibits superior efficiency over H-SELX (Luer-lock syringes LXA4 Emulsion loaded-Hydrogel). While both formulations stimulated pro-inflammatory cytokine secretion and promoted a pro-inflammatory macrophage phenotype, LXA4 emulsion-loaded hydrogels displayed a diminished pro-inflammatory activity compared to blank emulsion-loaded hydrogels. These findings highlight the biological efficacy of LXA4 within both systems, with H-SELX outperforming H-MELX in terms of efficiency. To the best of our knowledge, this is the first successful demonstration of the biological efficacy of LXA4 emulsion-loaded hydrogel systems on macrophage polarization. These versatile H-MELX and H-SELX formulations can be customized to enhance their biological activity making them promising tools to promote the resolution of inflammation in diverse clinical applications.

Development and In vitro Evaluation of a Nanoemulsion Containing Piroxicam for Topical Drug Delivery

ABSTRACT Background: A specific type of emulsion with a compatible droplet size of 20–500 nm and a submicron size range is termed nanoemulsion (NE), often referred to as mini emulsion. Nonsteroidal anti-inflammatory drugs such as piroxicam are employed to treat discomfort after surgery, acute gout, degenerative arthritis, and arthritis with inflammation. Objectives: With the aim of minimizing adverse medication reactions as well as enhancing compliance among patients, the study intends to develop and assess a piroxicam NE that includes oleic acid and Tween 80. It will do this by investigating the impact of the oil phase, surfactants, and cosurfactants on the product’s chemical and physical characteristics. Materials and Methods: After being homogenized, Tween 80, oleic acid, and paraffin oil are emulsified with ethanol and water. Zeta potential, drug entrapment efficiency, spreadability, viscosity, pH evaluation, and scanning electron microscopy (SEM) are being employed for the characterization of the dosage form. The procedure involves the dropwise addition of ethanol and continuous mixing. Results: According to accelerated experiments, four of the six formulations displayed good stability, suggesting their stability. This strategy is viable for NE formulations, with the entrapped drug percentage varying from 99.51 to 101.01. The range included additional factors such as drug release, texture, entrapment efficiency, spreadability, SEM zeta sizer, and polydispersity index value. Conclusions: Because of its potential negative effects, the study aimed to develop a stable NE of piroxicam for topical use by combining oleic acid, tween, paraffin, and ethanol. Because of their repelling characteristics, the charges strengthen stability, and the pH’s modest acidity helps to prevent skin infections. The study promotes spontaneous emulsification as the most suitable technique for producing NEs.

Formulation and evaluation of virgin coconut oil (VCO) lotion: Effect of variation in emulsifier type and concentration

Indonesia is a tropical country rich in agricultural commodities, such as coconut. One of the derived products from coconut is virgin coconut oil (VCO), which widely used as ingredient in cosmetic lotion products. This study aimed to evaluate the effects of variations in the addition of emulsifiers to VCO cream lotion. Two emulsifiers were used, including Tween 80 and Span 80 with concentrations of 5% without essential oil, 5%, 4%, 3%, and 2%. Quality parameters analyzed were homogeneity, specific gravity, stability, pH, and organoleptic. The data were statistically analyzed using the Kruskall-Wallis test. The results showed that Tween 80 and Span 80 emulsifiers significantly affected physicochemical and organoleptic characteristics, except pH value. The selected best formulation was cream lotion with the addition of 2% emulsifier formulation. This VCO lotion had a quality value according to SNI 16-4399-1996 and had organoleptic characteristics most preferred by the panelists.

Construction and Properties of O/W Liquid Crystal Nanoemulsion.

Liquid crystal emulsion is a new type of emulsion, in which the emulsifier molecules are located at the oil/water (O/W) interface and form a long-range ordered and short-range disordered lamellar liquid crystal. The lamellar liquid crystal formed by the emulsifier is similar to the skin stratum corneum lipid structure, which enables it to have a broad application prospect in the fields of cosmetics, pharmaceuticals, etc. In this work, a liquid crystal nanoemulsion was obtained by passing a liquid crystal emulsion stabilized by hydrogenated lecithin and phytosterol combination through a microfluidizer. The microstructure of the prepared liquid crystal nanoemulsion was investigated experimentally by dynamic light scattering, transmission electron microscopy, and small-angle X-ray scattering. The results have shown that the nanoemulsion inherited the liquid crystal emulsion property, namely, the long-range ordered and short-range disordered lamellar structure still existed at the oil/water interface even though they underwent extrusion, friction, and acceleration. At the same time, the underlying mechanisms of the existence of lamellar liquid crystal between the oil phase and the water phase for the nanoemulsion were explored theoretically by molecular dynamics simulations. The simulation results elucidated that the hydrogenated lecithin and phytosterol combination improved the flexibility of the bilayer structure composed of emulsifiers. The bilayers were the basic structure units of lamellar liquid crystals, and thus, the improved flexibility of bilayers provided insurance for the existence of lamellar liquid crystals with larger curvature around the oil droplets. In addition, the applicable properties of liquid crystal nanoemulsion were studied, and the results have shown that the liquid crystal nanoemulsion presented better slow-release and moisturizing properties than traditional nanoemulsions due to the existence of multilayers between oil and water phases. This work not only provides necessary information for the development and effective application of liquid crystal emulsions but also is helpful for in-depth understanding the inner properties of lamellar liquid crystal at molecular level.

Preparation and Performance Study of n-Undecane Phase Change Cold Storage Material.

With the fast development of the cold chain transportation industry, the traditional refrigeration method results in significant energy consumption. To address the national call for energy saving and emission reduction, the search for a new type of energy storage material has already become a future development trend. According to the national standard GB/T28577 for the classification and basic requirements of cold chain logistics, the temperature in frozen logistics is typically below -18 °C. In this study, n-undecane with a phase change temperature of -26 °C is chosen as the core material of microcapsules. Poly(methyl methacrylate) is applied as the shell material, with n-undecane microcapsules being prepared through suspension polymerization for phase change cold storage materials (MEPCM). Using characterization techniques including SEM, DSC, FTIR, and laser particle size analysis, the effects of three types of emulsifiers (SMA, Tween-80, Tween-80/span-80 (70/30)), SMA emulsifier dosage, core-shell ratio, and emulsification rate on the thermal performance and micro-surface morphology of n-undecane/PMMA microcapsules were studied. The results indicate that when comparing SMA, Tween-80, and Tween-80/span-80 (70/30) as emulsifiers, the dodecane/PMMA microcapsules prepared with SMA emulsifier exhibit superior thermal performance and micro-surface morphology, possessing a complete core-shell structure. The optimal microstructure and the highest enthalpy of phase change, measuring 120.3 kJ/kg, are achieved when SMA is used as the emulsifier with a quantity of 7%, a core-to-wall ratio of 2.5:1, and an emulsification speed of 2000 rpm. After 200 hot and cold cycles, the enthalpy of phase change decreased by only 18.6 kJ/kg, indicating the MEPCM thermal performance and cycle life. In addition, these optimized microcapsules exhibit favorable microstructure, uniform particle size, and efficient energy storage, making them an excellent choice for the refrigeration and freezing sectors.

Oil-in-water nanoemulsion adhesive system: Preparation by ultrasonic homogenization and its application in 3D direct writing composite energetic materials

Stable and low-particle size nanoemulsions were prepared using ultrasound homogenization. The conditions for preparing low-viscosity nanoemulsions were optimized using Response Surface Methodology (RSM) experimental design. The results showed that the addition of composite surfactants at 1%, an ultrasound amplitude of 35%, an ultrasound time of 4 min, and an ultrasound temperature of 20 °C yielded nanoemulsions with the best particle size and stability. The particle distribution was uniform, and the cold and heat stability were good. Compared with traditional emulsions, the low-viscosity nanoemulsion had better environmental stability, storage stability, and exhibited a phenomenon of self-reducing particle size at 40–55 °C, indicating that the emulsion had good performance under complex environmental conditions. The performance test of composite energetic materials using two types of emulsions as bonding systems showed that the low-viscosity nanoemulsion composite energetic material effectively reduced friction sensitivity, increased detonation velocity, and had better thermal stability and smaller propagation size. The results confirmed that the low-viscosity nanoemulsion perfectly met the requirements of bonding agents for composite energetic materials. This study provides a new approach for bonding agent systems of composite energetic materials and can serve as a new method to meet the special requirements of composite energetic materials.

Amplitude modulation in surfactant and polymer-based water-in-oil emulsions: A novel approach to enhance separation rate and mitigate chaining effects

Oil wells can eventually run out of oil if used for an extended period. Various polymers and surfactants are used to enhance oil recovery to extend the useful life of a well and improve the recovery process. These chemicals are added to make the extraction process easier. However, the emulsion that results from this process can be difficult to break down because of the added chemicals. Therefore, special measures are necessary to recover the crude oil effectively by breaking the emulsion. Electrocoalescers are specialized large-scale units designed for the purpose of separating water from emulsions. Improving the performance of an electrocoalescer involves achieving faster dehydration of the emulsion while ensuring safe operation. This means increasing the rate of water separation without compromising safety. The proposed technique aims to improve separation by modulation of the AC electric field. This modulation consists of a step with a high-amplitude electric field, followed by a step with a low-amplitude electric field, then repeated. This work involves a study of four types of emulsions that were used: (1) water-in-oil emulsion without surfactant/polymer, (2) polymer-stabilized water-in-oil emulsion, (3) surfactant stabilized water-in-oil emulsion, and (4) surfactant and polymer mixed-stabilized water-in-oil emulsion. The electrocoalescence process has faster kinetics compared to conventional methods. Modulation facilitates drop chaining during high voltage and effective coalescence during low voltage. It has been observed that an increase in the conductivity of the dispersed phase can lead to an increase in non-coalescence. The surfactant (SDS) and polymer (HPAM) mixture become more challenging to separate.

Oleic acid-modified layered double hydroxide for Pickering emulsions: (I) Interfacial properties

Layered double hydroxides (LDHs) are one type of potential emulsifiers for Pickering emulsions. Surface modification can regulate their surface properties, thereby affecting their emulsifying behavior. However, there is still a lack of full understanding of the impact of surface modification on their surface properties. In the current work, one Mg3Al-Cl LDH was modified using oleic acid (OA), obtaining six OA-modified products with different OA loadings. Their contact angles and relative dielectric constants were determined, and their surface properties including the interfacial free energies (γ) and solubility parameters (δ) were then estimated from the data. Their apparent molar volumes were estimated using the γ and δ data. OA molecules are coated on the LDH surface via the bidentate bonding mode to form monolayers. The OA modification has no obvious impact on the structure and morphology of LDH particles, but can significantly affect their surface properties. This work provides a better understanding of the dependence of surface properties of LDHs on the surface modification.

Novel activated biochar-enhanced superhydrophilic nanofibrous membrane for superior oil-in-water emulsion separation

In this research, a high-performance Polyamide 6/Polyvinyl Alcohol/Activated biochar (PA6/PVA/AB) composite nanofibrous membrane was developed for effective separation of oil-in-water emulsions. The membrane was produced by blend electrospinning of Polyamide 6 (PA6), Polyvinyl Alcohol (PVA), and Activated biochar (AB) derived from peanut shell biomass. Glutaraldehyde (GA) cross-linking was applied to enhance stability in aqueous environments to prevent PVA swelling. The resulting nanofibrous membrane exhibited a cost-effective design with a superhydrophilic/underwater superoleophobic surface (WCA of 0° and UWOCA of 164°), a porous structure (93% porosity), and robust mechanical properties (Tensile strength: 7.73 MPa, Young modulus: 45 MPa). Optimization of the membrane composition, with 5%wt. PVA and 2%wt. AB relative to the total polymer weight in the electrospinning solution, yielded a superhydrophilic membrane capable of withstanding 2 bar pressure. Pure water flux measurements in the pressure range of 0.5–2 bar demonstrated a high permeability of 1727.5 LMH/bar and a pure water flux of 3455 LMH. The PA6/PVA/AB composite membrane exhibited exceptional performance in separating non-surfactant (NS) and surfactant-stabilized (SS) toluene-in-water emulsions (separation flux: 2006 LMH, oil rejection: 99.52%). Furthermore, it demonstrated high efficiency in the separation of SS oil-in-water emulsions of different types of oil (separation flux >1800 LMH, oil rejection >98%). The membrane's durability and chemical stability were confirmed through 15 cycles of oil-in-water emulsion separation, showcasing anti-fouling properties and reusability (separation flux >833, Oil rejection >97%). Considering its superior performance in oil-in-water emulsion separation and robust reusability, the developed nanofibrous membrane holds significant promise for practical applications.

Incomplete lipid extraction as a possible cause for underestimation of lipid oxidation in emulsions

AbstractLipid oxidation deteriorates the sensory and nutritional quality of food emulsions containing polyunsaturated fatty acids. Classically, different extraction solvents are used as a first step to measure lipid oxidation in emulsions. However, it is unclear how the applied extraction method influences the measured lipid oxidation values. In this work, we systematically examined the performance of common solvent mixtures such as chloroform, methanol, and hexane (or isooctane)–isopropanol on lipid extraction from emulsions stabilized with different emulsifiers (Tween 20 (T20), whey proteins, and pea proteins) and oxidation levels, and how this, in turn, affected the measured hydroperoxide concentrations. Chloroform–methanol was the most effective solvent (lipid yield &gt;93 wt.%). When using hexane–isopropanol, extraction yields were consistently high for T20‐ and pea protein‐based emulsions (&gt;60 wt.%), but in whey protein‐based emulsions, values as low as 26 wt.% were measured. In case of incomplete extraction, hydroperoxide concentrations measured by colorimetric methods need to be corrected for this effect. When using 1H NMR to assess lipid oxidation, the actual amount of extracted lipids is intrinsically taken into account. This highlights not only the importance of the extraction method in determining lipid oxidation in emulsions but also that of the actual analysis method.Practical application: This study highlights that the lipid extraction yield can vary depending not only on the emulsion composition (e.g., type of emulsifier) but also on the oxidative state of the emulsion and the extraction solvent used. If this is overlooked, errors can be made in the hydroperoxide determination. Although these effects can be corrected for, this is not standard procedure, which implies that awareness on this matter should be increased. It is also important to point out that depending on the solvent used, the different lipid classes (including various lipid oxidation products) may be extracted at different levels. Chloroform–methanol should be preferred for extraction of all lipid and lipid oxidation‐derived molecules, including aldehydes.

Formulation and Characterization of Double Emulsions W/O/W Stabilized by Two Natural Polymers with Two Manufacturing Processes (Comparative Study)

Four distinct types of multiple emulsions were synthesized using xanthan gum and pectin through two distinct manufacturing processes. The assessment encompassed the examination of morphology, stability, and rheological properties for the resulting water-in-oil-in-water (W/O/W) double emulsions. Formulations were meticulously crafted with emulsifiers that were compatible with varying compositions. Remarkably stable multiple emulsions were achieved with a 0.5 wt% xanthan concentration, demonstrating resilience for nearly two months across diverse storage temperatures. In contrast, multiple emulsions formulated with a higher pectin concentration (2.75 wt%) exhibited instability within a mere three days. All multiple emulsions displayed shear-thinning behavior, characterized by a decline in apparent viscosity with escalating shear rates. Comparatively, multiple emulsions incorporating xanthan gum showcased elevated viscosity at low shear rates in contrast to those formulated with pectin. These results underscore the pivotal role of the stepwise process over the direct approach and emphasize the direct correlation between biopolymer concentration and emulsion stability. This present investigation demonstrated the potential use of pectin and xanthan gum as stabilizers of multiple emulsions with potential application in the pharmaceutical industry for the formulation of topical dosage forms.

Importance of emulsifiers in chocolate industry: Effect on structure, machinability, and quality of intermediate and final products

AbstractMany parameters are effective in obtaining optimum rheological and sensory properties in chocolate. Lecithin, ammonium phosphatides (AMP), and less commonly glycerol monopalmitate (GMP) are typically used as emulsifiers to achieve the desired viscosity in chocolate. In addition to these emulsifiers, polyglycerol polyricinoleate (PGPR) is used as a complement to regulate the yield value in chocolate. In this review, the properties of these additives, their interactions with each other, and the mechanism of their structural improvement functions in chocolate production are discussed. Depending on the type and amount of emulsifier, adjustments can be made to the flow behavior of molten chocolate, textural, melting character, tempering and tempering index, color and other properties of the chocolate. In addition to the use of emulsifiers, other parameters such as particle size distribution, moisture and fat content should also be taken into account, which can affect all these quality parameters. In this regard, the correct selection of the type of emulsifiers used in chocolate production and their combined usage rates will ensure that the demands of producers and consumers are met.

Effects of Maillard reaction of different monosaccharide-modified on some functional properties of fish gelatin

In this work, the effects of Maillard reaction of different monosaccharide-modified fish gelatin were studied. The changes of gel properties, rheology and structure of fish gelatin before and after modification were compared and analyzed, and oil-in-woter emulsions were prepared. The results showed that the five-carbon monosaccharide had stronger modification ability than the six-carbon monosaccharide, which was mainly due to the different steric hindrance of the amino acids in the nuclear layer and the outer layer to the glycosylation reaction. With the progress of the Maillard reaction, the color of fish gelatin gradually became darker. The attachment of sugar chains inhibited the gelation process of fish gelatin, decreased the gelation rate, changed the secondary structure, increased the content of β-turn or α-helix, increased the degree of fluorescence quenching, and enhanced the emulsifying properties and emulsion stability. This study provides useful information for the preparation of different types of monosaccharide-modified proteins and emulsions.

Justification of the composition of the base of the emulsion ointment for the fungal diseases skin treatment

The relevance and socio-economic significance of the problem is determined by the prevalence of fungal diseases, which are affected by every fifth inhabitant of the planet (according to the World Health Organization). Among fungal diseases, dermatomycoses, which are complicated by infection and keratization of the skin, are of particular importance.&#x0D; In the treatment of dermatomycoses, a significant place belongs to external therapy (soft and liquid medicinal products). Dermatological medicinal products in Ukraine are mainly represented by drugs of foreign production – 58.2%.The range of multicomponent drugs affecting all links of the pathological process is 21%. Therefore, the development of a scientifically based composition and technology of a multicomponent soft medicine for the treatment of dermatomycoses is an urgent problem of our time.&#x0D; The goal of our research was to develop the optimal composition of the emulsion ointment base for the treatment of fungal skin diseases.&#x0D; The objects of the study were combinations in different ratios of surface-active substances, hydrophilic non-aqueous substances and emulsifiers. The osmotic properties of the experimental bases were studied using dialysis through a semipermeable membrane. The study of the rheological properties of the samples was carried out on a rotary viscometer Reotest-2 (USA) with a water circulation heater. Determination of colloidal stability (for emulsion systems) was carried out according to DSTU 4765:2007 «Cosmetic creams. General technical conditions». Determination of thermal stability was carried out according to DSTU 4765:2007 «Cosmetic creams. General technical conditions».&#x0D; Based on the conducted experimental studies, the composition of the base of the emulsion ointment was substantiated. Rheological studies have established the optimal concentration of surface-active substances in emulsions. The study of the osmotic activity of model emulsions made it possible to establish the optimal ratio of hydrophilic-non-aqueous solvents in the composition of model samples.&#x0D; On the basis of the conducted structural-mechanical and pharmacological studies, the composition of the emulsion base of the o/w type emulsion ointment was substantiated for treatment of fungal skin lesions: petroleum jelly (20.0 g), emulsifier No. 1 (5.0 g), PEO-400 (5.0 g), glycerin (5.0 g), Na-KMC (1.0 g), purified water up to 100.0 g.

Oleic acid-modified layered double hydroxide for Pickering emulsion: (II) Emulsification behavior

Layered double hydroxides (LDHs) are plate-like particles, being potential Pickering emulsifiers. Surfactant modification can regulate their surface properties, and thus can influence their emulsifying behavior. However, there is a lack of full understanding on the correlation between the surface modification of LDHs and their emulsification behavior. In the current work, one LDH and five oleic acid (OA)-modified LDH (LDH@OA) samples were chosen as emulsifiers, and emulsifying tests for pentadecane (oil)-water mixtures were performed at different oil/water volume ratios (1/9−9/1) and solid dosages (Cs, 1.00−10.0 g/L). The type, droplet size, and stability of emulsions were determined. The interfacial adsorption energy (ΔGad) and the coverage of solid particles for droplet surfaces (Rcov) were estimated, and the oil-water interfacial tension and viscoelastic moduli were determined. Results showed that LDH and LDH@OA particles can emulsify the oil-water mixture, forming coalescence-stable Pickering emulsions. The emulsion type is only determined by the solid wettability, independent of the oil/water ratio and Cs. The OA modification can change the wettability of LDH from hydrophilic to hydrophobic, thereby can regulate the type of emulsions from oil-in-water (O/W) to water-in-oil (W/O). Enhancing solid hydrophobicity decreases droplet sizes and increases interfacial viscoelasticity, thus improving the stability of emulsions. The droplet size decreases with an increase in Cs, while it increases with an increase in the volume fraction of dispersed liquid, both independent of the type of emulsions. The solid particles can irreversibly adsorb at the oil-water interface (with |ΔGad|/kT > 107), forming interfacial particle-layers with Rcov ∼0.4 and strong viscoelasticity, which endow the Pickering emulsions with extremely strong stability against coalescence.

Dual functionality of diacylglycerols in water-in-oil emulsion gel systems

Distearin (DS) can be used as an emulsifier, due to its surface activity derived from the amphiphilic nature of the molecule, moreover, it can also crystallize and form a 3D crystal network that can induce oil gelation. The current research aimed to examine the ability to combine both emulsifying and oil gelation properties to structure and stabilize water-in-oil emulsion gel system. Different water contents and DS concentrations produce emulsion gels with different textural attributes while incorporating up to 30% of water in a 15% wt. DS-based oleogel resulted in stable white gels. Microscopy imaging confirmed the formation of a water-in-oleogel type emulsion gel characterized by DS crystallization in the continuous phase and at the interface through Pickering mechanism. A positive relation was observed between the G′ and hardness values and water content, suggesting gel strengthening resulted from interactions between the DS crystals at the interface and the continuous phase, as suggested by the active filler theory. Thermal analysis revealed two broad melting events at the temperature range of 42.2–44.9 °C and 55.9–58.6 °C for emulsion gels with 10–30% water content, suggesting initial melting of β' polymorph and transition to β during melting, which was confirmed by XRD. The results showed that homogenization significantly improved the oil retention of the gels due to increased crystal surface area, while water addition slightly reduced it. Compared with traditional emulsions or oleogels, this water-in-oil gel system demonstrated prolonged stability and enhanced mechanical properties due to the dual functionality of DS at the water/oil interface and bulk.

Amphiphilic Covalent Organic Framework Nanoparticles for Pickering Emulsion Catalysis with Size Selectivity

AbstractExploiting advanced amphiphilic solid catalysts is crucial to the development of Pickering emulsion catalysis. Herein, covalent organic framework (COF) nanoparticles constructed with highly hydrophobic monomers as linkers were found to show superior amphiphilicity and they were then developed as a new class of solid emulsifiers for Pickering emulsion catalysis. Employing amphiphilic COFs as solid emulsifiers, Pickering emulsions with controllable emulsion type and droplet sizes were obtained. COF materials have also been demonstrated to serve as porous surface coatings to replace traditional surface modifications for stabilizing Pickering emulsions. After implanting Pd nanoparticles into amphiphilic COFs, the obtained catalyst displayed a 3.9 times higher catalytic efficiency than traditional amphiphilic solid catalysts with surface modifications in the biphasic oxidation reaction of alcohols. Such an enhanced activity was resulted from the high surface area and regular porous structure of COFs. More importantly, because of their tunable pore diameters, Pickering emulsion catalysis with remarkable size selectivity was achieved. This work is the first example that COFs were applied in Pickering emulsion catalysis, providing a platform for exploring new frontiers of Pickering emulsion catalysis.