Interdroplet Interactions Research Articles

Interfacial rheological properties of pepsin-hydrolyzed lentil protein isolate at oil-water interfaces

Lentil protein isolate (LPI) was investigated for its potential as a plant protein-based emulsifier. LPI consists mainly of globulins with high molecular weights which are relatively slow to adsorb and stabilize oil-water interfaces. Smaller proteins, such as whey protein, can stabilize the interface much faster, quickly forming a viscoelastic film that slows down the rate of droplet recoalescence, leading to smaller droplets. To increase the rate of adsorption, LPI was enzymatically hydrolyzed by pepsin at 1.5% and 4.5% degree of hydrolysis (DH), to obtain small peptides. The behavior of these peptides was studied at the oil-water interface in comparison to whey protein isolate (WPI) and native lentil protein isolate (LPI). Interfacial properties were investigated using dilatational and interfacial shear rheology in the linear viscoelastic regime (LVE) and nonlinear viscoelastic regime (NLVE) and these were related to protein characteristics and emulsion formation. The 1.5% and 4.5%DH LPI showed high surface hydrophobicity, and consisted mainly of low molecular weight peptides, which contributed to faster adsorption kinetics and consequently covered the interface faster than LPI. In dilatation, the native and hydrolyzed LPI-stabilized interfaces had comparable stiffness and were clearly weaker than WPI-stabilized interfaces, which contrasts with the results in shear deformations, where the former both had higher stiffness than WPI. Both hydrolyzed LPI and WPI formed more brittle and less stretchable interfaces compared to native LPI in both dilatational and shear rheology. In emulsification tests, native LPI produces the largest droplets, and the 4.5% DH LPI and WPI have the smallest droplet size. But, bridging flocculation was observed when emulsions were prepared with both hydrolyzed LPI, which may be attributed to inter-droplet hydrophobic interactions between small polypeptides. This can be linked to an increase in the surface hydrophobicity of hydrolyzed LPI. Thus, the use of native LPI as a stabilizer in emulsion preparation is preferable over the hydrolyzed samples, despite its larger droplet size.

Phosphorylation altered structural flexibility of goose liver protein: Relation to interfacial and emulsifying properties

This work elucidated the roles of ultrasonication (GLP-U), phosphorylation (GLP-S) and their combination (GLP-US) on the emulsifying properties of goose liver protein (GLP-N) from an interfacial perspective. Results of interfacial pressure (11.98 ± 0.24 mN/m) and elastic modulus (10.63 ± 0.12 mN/m) showed that combined ultrasonication and phosphorylation rendered the highest interfacial interaction of GLP-N by facilitating its structural flexibility. Microrheology and multiple light scattering indicated that the enhanced electrostatic repulsion among GLP-US favored the interdroplet dissociation. Consequently, both the droplet size and flocculation index of emulsions were markedly decreased using either low (19.53 μm ± 1.06 and 8.18%) or high particle concentration (7.75 ± 0.24 μm and 6.85%) of GLP-US when compared with the sole treated groups and the control. Overall, phosphorylation fortified the intradroplet protein-protein interaction but restrained the interdroplet interaction of GLP-N, and the assistance of ultrasonication endowed the protein with enhanced interfacial stabilization and emulsifying efficiency.

Refractive-index and density-matched emulsions with programmable DNA interactions.

Emulsion droplets on the colloidal length scale are a model system of frictionless compliant spheres. Direct imaging studies of the microscopic structure and dynamics of emulsions offer valuable insights into fundamental processes, such as gelation, jamming, and self-assembly. A microscope, however, can only resolve the individual droplets in a densely packed emulsion if the droplets are closely index-matched to their fluid medium. Mitigating perturbations due to gravity additionally requires the droplets to be density-matched to the medium. Creating droplets that are simultaneously index-matched and density-matched has been a long-standing challenge for the soft-matter community. The present study introduces a method for synthesizing monodisperse micrometer-sized siloxane droplets whose density and refractive index can be precisely and independently tuned by adjusting the volume fraction of three silane precursors. A systematic optimization protocol yields fluorescently labeled ternary droplets whose densities and refractive indexes match, to the fourth decimal place, those of aqueous solutions of glycerol or dimethylsiloxane. Because all of the materials in this system are biocompatible, we functionalize the droplets with DNA strands to endow them with programmed inter-droplet interactions. Confocal microscopy then reveals both the three-dimensional structure and the network of droplet-droplet contacts in a class of self-assembled droplet gels, free from gravitational effects. This experimental toolbox creates opportunities for studying the microscopic mechanisms that govern viscoelastic properties and self-assembly in soft materials.

Cultivating edible bio-inks: Elevating 3D printing with medium-internal-phase emulsion gel incorporating soybean protein isolate microgel particles

In response to changing dietary preferences and increasing health consciousness among consumers, the food industry is gradually moving toward healthier and higher-performance edible bio-inks. This study prepared soybean protein isolate microgel particles (SPIMP) using dynamic high-pressure microfluidization (DHPM) as a pretreatment method. Under DHPM pressure, the average particle size of SPIMP progressively decreased from 609.6 nm to 254.8 nm, accompanied by an increased interfacial adsorbed protein content of 81.78% and 91.49%. Contact angles of native SPI were measured at 70.1° ± 0.6°, while those for microgel particles were 78.1° ± 0.2°, 80.3° ± 0.7°, and 84.5° ± 1.2°, respectively. These SPIMP were then utilized to formulate a medium-internal-phase emulsion gel with an oil fraction of 50%. Microscopic analysis and examination of chemical interaction forces revealed that the network structure of the emulsion gel primarily formed through inter-droplet hydrophobic interactions and the formation of disulfide bonds. This enhancement contributed to the gel strength and water retention capacity of the emulsion. Rheological tests confirmed the outstanding shear-thinning properties and high viscoelasticity of the emulsion gel, positioning it as a promising edible bio-ink for 3D printing. Experimental printing further substantiated its suitability, confirming extrudability, printing performance, and self-supporting properties. Notably, the medium-internal-phase emulsion gel-based reduced-fat surimi products demonstrated better suitability for 3D printing within real food systems compared to traditional surimi products. This study introduced innovative approaches for producing medium-internal-phase emulsion gel with superior 3D printing properties, significantly expanding the potential for the development of edible bio-inks.

Anti-Alzheimer Drug Delivery via Pickering Emulsions Stabilized by Plate-like Cellulose Nanocrystals.

In this work, we studied for the first time the formation of olive oil emulsions in water stabilized by plate-like nanocrystals with the supramolecular structure of cellulose II (pCNC). Effects of storage, pCNC concentration, and NaCl on the stability and properties of Pickering emulsions, including the creaming index, droplet size, zeta potential, acid-base surface properties, and rheology, were studied. A significant influence of the shape of nanoparticles (compared to the classical rod-like shape) on the stability parameters and rheological characteristics of emulsions is shown. Plate-like cellulose nanocrystals at a concentration of 16 g/L are able to form delamination-resistant emulsions without added electrolytes. The viscosity of pCNC-stabilized emulsions tends to decrease with increasing electrolyte concentration in the system, which is not characteristic of rod-like CNC-stabilized emulsions. This effect in pCNC-stabilized emulsions assumedly can be associated both with weak mechanical engagement between drops due to the shape of stabilizer particles and with an insignificant participation of background electrolyte cations in the formation of interdroplet interactions. Therefore, the resulting aggregates are unstable and easily destroyed, even under weak mechanical stress. As a consequence, the acid-base properties of the pCNC surface are practically independent of the emulsion preparation method (with or without electrolyte) as well as the concentration of the background electrolyte. The reduced viscosity of pCNC-stabilized emulsions in the presence of an electrolyte, coupled with the absence of acute toxicity, allows us to recommend them as a convenient oral delivery system for fat-soluble, biologically active substances. Our emulsions carrying donepezil (an anti-Alzheimer drug) showed better performance than a solution of donepezil hydrochloride in preventing memory impairment tested on laboratory mice.

Control of pore interconnectivity in emulsion-templated porous polymers

The applications of porous polymers obtained from polymerized high internal phase emulsions (polyHIPEs) depend on their morphology, especially interconnectivity of pores (openness). For example, an open-cell structure is required for filtration and adsorbent materials, whereas a closed-cell structure is ideal for the applications in energy storage, insulation, and encapsulation. However, the remaining challenge is to control the interconnectivity of polyHIPEs, which is influenced by the complex process of pore throat formation. In this work, we demonstrate that the formation of pore throats can be tuned through varying the attractive interdroplet interactions in the HIPE precursor. The attractive interactions among the droplets are manipulated by employing different surfactants and the refractive index (RI)-matching agent. While the depletion attraction and steric repulsion can be indirectly controlled by changing the surfactant, the van der Waals interaction is controlled by varying the amount of RI-matching agent. The scaled viscoelastic moduli of HIPEs with Laplace pressure are used to further confirm the variation of interdroplet interactions. In addition to the interdroplet interactions, we investigate the potential effect of interfacial rheology on the interconnectivity of polyHIPEs.

Destabilization of oil-in-water emulsions: Influences of interfacial assembly of octenyl succinic anhydride starch and chitosan

This study investigated the formation and destabilization of emulsions with different interfacial assemblies of octenyl succinic anhydride starch (OSAS) and chitosan (CS) at critical pH values. All emulsion droplets were connected to each other via bridging of interfacial percolation and observed to form gel network structures during prolonged storage. In addition, partial pH-dependent flocculation occurred during preparation and decreased the degree of coalescence and creaming of emulsions. Compared to bilayer (OSAS-CS and CS-OSAS) emulsions, the complex (OSAS/CS)-stabilized emulsions were more resistant to coalescence, creaming, and lipid oxidation because of their thick interfacial layers (∼2 μm) and tight percolation networks. The layer-by-layer adsorption of OSAS and CS at the interface may lead to reduced homogeneity and stability of the bilayers, making them relatively susceptible to destabilization. Moreover, an appropriate pH (6.0) facilitated the oxidation stability of emulsions by influencing inter-droplet electrostatic interactions. For complex-stabilized emulsions, the lipid hydroperoxide content at pH 6.0 was reduced by approximately 22.85% and 12.26% respectively compared with that at pH 5.5 and pH 6.5. This work may provide promising insights into the rational design of emulsions with desirable stability by combing biopolymers.

Solid-like elastic behavior of nanosized concentrated emulsions: Size-dependent Young’s and bulk moduli

Concentrated emulsions with volume fractions exceeding the critical value have diverse applications in foods, cosmetics, coatings, and pharmaceuticals. They have a jammed structure and tend to exhibit a solid-like behavior. Unfortunately, the mechanical properties of monodisperse concentrated emulsions are challenging to study by experiments or simulations because of thermodynamic instability and droplet coalescence. A mesoscopic simulation method is employed to study the mechanical properties of the concentrated emulsion. Knowledge of the microstructure and interdroplet interaction among monodisperse droplets is not a prerequisite. Effects of the volume fraction (ϕ), droplet diameter (D), and interfacial tension (σ) on Young’s modulus (E) and bulk modulus (K) are investigated systematically. For ϕ < ϕc, Young’s modulus is absent and the bulk modulus rises with increase ϕ. For ϕ > ϕc, both Young’s and bulk moduli are found to grow with increasing ϕ and σ. However, these solid-like properties become more prominent as D is decreased. On the basis of the interfacial energy per unit volume, our simulation results can be well represented by the relations E ∼ ϕ0.13(ϕ-ϕc)1.55(σ/D) and K ∼ ϕ1.06(ϕ-ϕc)0.15(σ/D). Moreover, the relationship for soft materials E = 3 K(1 − 2ν) is satisfied. The Poisson’s ratio (ν) is very close to 0.5 but still decreases slightly with increasing ϕ.

Rheological study of nanoemulsions with repulsive and attractive interdroplet interactions.

Nanoemulsions have adjustable transparency, tunable rheology, high stability, and low sensitivity to changes in pH and temperature, which make them interesting for applications such as low-fat and low-calorie foods. In this research, we study model concentrated nanoemulsions which are stabilized by sodium dodecyl sulfate (SDS). To prepare samples in different structural states, semi-dilute nanoemulsions are prepared at 25% droplet volume fraction (φ), after which evaporating the continuous phase at room temperature leads to concentrated nanoemulsions up to 60% volume fraction. Surfactant concentration is also tuned to induce different interdroplet interactions so that concentrated nanoemulsions in repulsive glass, attractive glass, and gel states are achieved. Rheological properties of nanoemulsions with different structural states are comprehensively studied over a volume fraction range. Utilizing the existing predictive models for (nano)emulsion rheology reveals a more satisfactory prediction for repulsive systems than systems with attractive interactions. In addition, a master curve is constructed for storage and loss moduli of nanoemulsions with different interdroplet interactions. The present work offers control over physicochemical properties of nanoemulsions for design of new food products with enhanced quality and functionality.

Glassy and compressed nanoemulsions stabilized with sodium dodecyl sulfate in the presence of poly(ethylene glycol)-diacrylate.

The rheology of concentrated nanoemulsions is critical for their formulation in various applications, such as pharmaceuticals, foods, cosmetics, and templating advanced materials. The rheological properties of nanoemulsions depend on interdroplet interactions, Laplace pressure, dispersed phase volume fraction, and continuous phase properties. The interdroplet forces can be tuned by background electrolytes (i.e., charge screening), surfactant type, the excess surfactant micelle concentration, and depletant molecules such as polymer chains. In the current research, we study the effect of varying the content of poly(ethylene glycol)-diacrylate (PEGDA) on the interfacial tension of the water-oil phase and rheological properties of concentrated nanoemulsions with 50% and 60% volume fractions. Sodium dodecyl sulfate (SDS) is used as the ionic surfactant. The final concentrated nanoemulsions are repulsive according to overall interaction potentials and are in the glass and compressed states based on the effective volume fraction estimation. They contain nearly same SDS concentration on the droplet surface and also in the bulk, but a different amount of PEGDA. The scaled rheological properties of the glassy nanoemulsions show a higher dependency on the PEGDA content and the possible effect of polymer-surfactant complexations compared to those of the compressed ones. This dependency is more pronounced in small strain amplitudes but not in large strains in the non-linear regime. These results provide insights into formulating concentrated nanoemulsions with controlled rheology for expanded application areas.

Analysis of the correction factors and coupling characteristics of multi-droplet evaporation

During the multi-droplet evaporation, the droplet interactions slow down the droplet evaporation. Historically, the evaporation processes have been studied mainly based on modifying the isolated droplet evaporation model. The actual multi-droplet evaporation can influence the three-dimensional flow field. However, it is not easy to replace the evaporation progress with the simplified model of the isolated droplet. Due to the complexity of the heat and mass transfer mechanism of the multi-droplet evaporation, the microscopic and accurate experiments are challenging to carry out, which leads to that the existing models are primarily derived from the theoretical aspects. In the present paper, the multi-droplet evaporation systems are simplified as different droplet arrays and reproduced based on the point source method (PSM) by introducing a correction factor to evaluate the inter-droplet interaction. The correction factor is numerically obtained, compared and validated. The parameter sensitivity of the correction factor is conducted systematically. In addition, the influence threshold is introduced to consider the droplet-gas coupling interactions. Thus, the local effects due to the transient evaporation of droplets are corrected. The results reveal that there exists a critical spacing used to determine whether the droplet interactions can be neglected. Additionally, droplets with larger sizes and smaller spacing dominate the inhibitory effect on the studied droplet. Finally, the correction for local effects will significantly reduce the droplet transient evaporation calculation error.

Packing microstructures and thermal properties of compressed emulsions: Effect of droplet size

In preparing thermodynamically metastable emulsions, the droplets tend to coalesce. Consequently, it is difficult to investigate the properties of a monodisperse compressed emulsion experimentally or by simulations. At a specified volume fraction, the properties of emulsions vary with the droplet size but the relevant studies are very limited. The dissipative particle dynamics simulations are adopted to explore the highly concentrated emulsion of monodisperse droplets. Prior knowledge of the microstructure and inter-droplet interaction is not required. The critical packing associated with the onset of the jammed structure can be identified from the growth of the projected area and perimeter of droplets with the volume fraction (ϕ), ϕc ≈ 0.65. The mean coordination number (Z) from the radial distribution function rises with increasing the volume fraction, and can be described by the scaling relation (Z-Zc) ∼ (ϕ-ϕc)0.82 with Zc ≈ 6.3. The effects of the volume fraction, droplet diameter (D), and interfacial tension (σ) on the internal energy (U) and heat capacity (Cv) are studied systematically. Both U and Cv are found to grow as ϕ and σ are increased but D is decreased. According to dimensional analysis, all the data points can be well represented by the scaling relations (Cv − Cv,c) ∼ ϕ(ϕ − ϕc)1/3(σ/D) and (U − Uc) ∼ ϕ(ϕ − ϕc)1/3(σ/D).

Measurement of interacting ethanol droplets evaporation at moderately elevated temperature and pressure using phase rainbow refractometry

Evaporation characteristics of interacting fuel droplets under the joint effect of ambient pressure, temperature and droplet size and spacing are critical to combustor design and simulation validation. This work reports an experimental study of evaporating monodisperse ethanol droplets at moderately elevated temperature (up to 673 K) and pressure (0.1-1.0 MPa). Evolution of droplet size and temperature along the measurement line and its evaporation rate were simultaneously measured using recently developed phase rainbow refractometry. The respective effects of the ambient conditions and droplet interactions on the heat and mass transfer of droplets were jointly studied. The results suggest that at lower ambient temperatures the droplet evaporation rate decreases with increasing ambient pressure. While at higher temperatures, the trend is reversed. Moreover, the dimensionless spacing parameter C of the droplets was well controlled to investigate the effect of inter-droplet interactions on evaporation under different ambient conditions. Strong droplet interactions, significantly inhibiting the droplet evaporation, were found to be influenced by ambient pressure. For the specific condition of droplet evaporation under low ambient temperature (373 K) and high pressure (1.0 MPa), the evaporation rate of droplets with C = 1.85 decreases by 19.1 % compared to droplets with C = 3.73. Furthermore, the correlations for Nusselt and Sherwood numbers are inferred by parametric study of the influence of the involved characteristic numbers.

Confined flow behavior under high shear rates and stability of oil/water high internal phase emulsions (HIPEs) stabilized by whey protein isolate: Role of protein concentration and pH

High shear rheometry was used to investigate the rheological behavior of high internal phase emulsions (HIPEs) stabilized by whey protein isolate (WPI). The physical stability of HIPEs was tested at extremely high shear rates generated by decreasing the gap height between parallel plates. Viscosity and yield stress, at narrow gaps, increased with protein concentration due to tighter packing of smaller droplets. Structural breakdown and recovery of HIPEs were affected by protein concentration and pH. The hysteresis behavior of HIPEs was either thixotropic or anti-thixotropic and was determined by protein concentration, whereas pH affected the magnitude of anti-thixotropy. At pH 3, emulsions showed greater stability against extreme shear and creaming due to higher deformability of oil droplets and increased interdroplet interaction compared to neutral pH. Challenging the physical integrity of concentrated emulsions under high shear is an effective way to characterize microstructural changes and stability of HIPEs in foods.

Self-propulsion dynamics of nanosized water droplets on MoS2/graphene heterojunction surface: A molecular dynamics simulation study

Controlling the self-propelling of nanosized colloids at the heterogeneous surface is of great importance to various conventional and emerging applications. Herein, molecular dynamics simulations are performed to study the spontaneous self-propulsion dynamics of nanosized water droplets (NWDs) at the MoS2/graphene heterojunction surface, which demonstrates the propulsion of a single NWD is similar to a locomotive towing train carriage that occupies the contact area of a wetting surface robustly, thus facilitating the self-propulsion dynamics energetically and thermodynamically. The average self-propelled velocity of a single NWD can reach 5 m/s driven by the surface wettability difference. Interestingly, the propulsion of double NWDs is similar to a gluttonous snake motion, and the average velocity of the NWDs can be improved up to 6.0–9.0 m/s, which is attributed to the inter-droplet interactions derived by hydrogen bonds between the two NWDs. Besides, the diffusion of NWDs is a typical isotropic motion rather than isotropic immigration, which signifies that the self-propelled NWD can be exploited as a detecting motor or navigator in the future. Our findings provide fundamental insights into the molecular mechanism of NWD self-propulsion on a heterojunction surface, and the results could facilitate the design and fabrication of heterojunction surfaces for self-propelled NWDs

Freeze-thaw-stable high internal phase emulsions stabilized by soy protein isolate and chitosan complexes at pH 3.0 as promising mayonnaise replacers

The development of cholesterol-free mayonnaise has attracted increasing interest in the food colloid field, due to the potential health concerns as a result of consumption of cholesterol-rich mayonnaise. One effective strategy in this regard is to substitute or partially substitute egg yolk with other organic emulsifiers and stabilizers, without affecting the quality of the product. In the work, we reported an effective strategy to fabricate high freeze-thaw-stability high internal phase emulsions (HIPEs), using complexes of a heated soy protein isolate (SPI) and chitosan (CS) at pH 3.0 as the emulsifiers and stabilizers. The SPI/CS complexes, formed even at a very low CS-to-SPI ratio, e.g., 1:10, showed a high capacity to stabilize HIPEs with a high freeze-thaw stability. Increasing the CS-to-SPI ratio in the complexes resulted in a progressive strengthening of gel network in the corresponding HIPEs, together with a gradual improvement of emulsification performance. The gel network of the HIPEs stabilized by the SPI/CS complexes was mainly maintained by the inter-droplet noncovalent interactions involving the CS molecules. The presence of CS also progressively increased the percentage of adsorbed proteins at the interface, and decreased the surface coverage of proteins at the interface. The high freeze-thaw stability of such HIPEs might be unrelated to the ice crystal formation during the freezing, and was more likely associated with the strong steric repulsion contributed to the adsorbed CS molecules between different droplets. The results indicated that the complexation of heated SPI and CS could provide an effective strategy to facilely fabricate outstanding freeze-thaw-stability HI PEs as potential mayonnaise replacers.

Nanoemulsion polymerization and templating: Potentials and perspectives

The current study aims to provide an outlook on the nanoemulsions templating method by discussing their potentials to produce different polymers and evaluating challenges that might be posed during emulsification and polymerization. Tunable properties such as controllable droplet size, volume fraction, composition, and interdroplet interactions provide tools for controlling the structure of nanoemulsions and nanoemulsion-templated polymers. Therefore, these properties along with a phase diagram including the liquid, gel, attractive glass, and repulsive glass states of nanoemulsions are discussed in this Perspective. Although the synthesis of nanoparticles is the main application of nanoemulsion templating in the literature, polymerization of monomers in the continuous phase of nanoemulsions has potential to expand their applications and produce complex structured porous polymers. Nanoemulsion characteristics can also be tuned to produce porous polymers with desirable properties. This Perspective also looks at multiple nanoemulsions with multi-phase droplets, which recently have become of great interest for producing nanoparticles with complex morphologies. Multiple nanoemulsions and their templating provide new avenues for certain applications particularly in pharmaceutical and nanotechnology industries.

Low-oil-phase emulsion gel with antioxidant properties prepared by soybean protein isolate and curcumin composite nanoparticles

A low-oil-phase emulsion gel (Φ < 0.3) was prepared via high-pressure homogenization (HPH) of composite nanoparticles of soybean protein isolate (SPI) with different curcumin concentrations. Native-PAGE electrophoresis, fluorescence spectroscopy, and Fourier-transform infrared spectroscopy demonstrated that the SPI and curcumin were bound by hydrophobic interactions within the nanoparticles (SPI-Cur-NPs). The three-phase contact angle (θo/w) was altered by the addition of curcumin, and the particles exhibited outstanding wettability (θo/w = 80.6 ± 1°) at a curcumin concentration of 50 μM. According to the confocal laser scanning microscopy and cryo-scanning electron microscopy images, the network of emulsion gels with an oil phase of 30% was mainly composed of compact “aggregated” oil droplets, which were mainly formed due to inter-droplet hydrophobic interactions. The formation of such a gel network and the addition of curcumin avoided oxidative deterioration, and maintained a lower peroxide value, which was 1.8 times lower than that of the blank control group during the 30-day storage experiment. Moreover, the peroxide value of this gel was maintained at approximately 0.118 μmol/L during the 14-day accelerated oxidation experiment. Therefore, the low-oil-phase-emulsion gels stabilized by SPI-Cur50-NPs may be used to protect easily oxidized-lipid-soluble nutrients in a low-fat diet.

Attractive Pickering Emulsion Gels.

Properties of emulsions highly depend on the interdroplet interactions and, thus, engineering interdroplet interactions at molecular scale are essential to achieve desired emulsion systems. Here, attractive Pickering emulsion gels (APEGs) are designed and prepared by bridging neighboring particle-stabilized droplets via telechelic polymers. In the APEGs, each telechelic molecule with two amino end groups can simultaneously bind to two carboxyl functionalized nanoparticles in two neighboring droplets, forming a bridged network. The APEG systems show typical shear-thinning behaviors and their viscoelastic properties are tunable by temperature, pH, and molecular weight of the telechelic polymers, making them ideal for direct 3D printing. The APEGs can be photopolymerized to prepare APEG-templated porous materials and their microstructures can be tailored to optimize their performances, making the APEG systems promising for a wide range of applications.

Rheology of macro- and nano-emulsions in the presence of micellar depletion attraction

In this work, we investigate the effect of interdroplet interaction on the rheological behavior of oil-in-water emulsions within a range of macro- to nano-droplet sizes and various volume fractions from dilute to concentrated regimes. We determine the total interdroplet interaction from electrostatic, van der Waals, and depletion attraction contributions. At constant surfactant concentration, the depth of attractive potential is much higher than kBT for submicron emulsions and macroemulsions, whereas it is on the order of thermal energy for nanoemulsions. Thus, as the droplet size decreases in systems with considerable yield stress below jamming transition, the emulsions undergo a gel-to-glass transition. The yield strain ranges of gel and glassy systems overlap, although the droplets in gels undergo the dissipative rearrangement before macroscopic translational motion.