Pickering Emulsion Template Research Articles

Preparation and oil absorption performance of ATP/P(MMA-BMA-St)/Fe

In this paper, oil-in-water-in-oil (O/W/O) double Pickering emulsions were prepared by purified and modified attapulgite (ATP), and modified nano-Fe3O4 as stable particles. By using the Pickering emulsion as a template and using methyl methacrylate (MMA), butyl methacrylate ester (BMA) and styrene (St) as monomers, ATP/P(MMA-BMA-St)/Fe3O4 composite porous resins were then prepared. The oil absorption performance of the composites was investigated. The results showed that the composite materials prepared by the double Pickering emulsion template method exhibited a three-dimensional (3D) porous structure. When using the optimal conditions (mMMA:mBMA = 3:2, m(MMA+BMA):mSt = 1:2, initiator = 5.33%, crosslinking agent = 20%, modified attapulgite = 0.33% and oil phase/water phase = 1:4), the prepared porous material had the best oil absorption performance, resulting in a diesel oil absorption rate and oil retention rate of 897.29 and 84.76% respectively. This study provides a simple, economic and environmentally friendly method for the preparation of inorganic–organic composite porous materials, which has great application potential in the field of oil treatment.

Fabrication PDA-polyurea microcapsules with anti-photolysis and sustained-release performances via Pickering emulsion template

Fabrication PDA-polyurea microcapsules with anti-photolysis and sustained-release performances via Pickering emulsion template

Optimization of Conditions for Preparation of Ginger Essential Oil Microcapsules by Acid-Modified Palygorskite-Stabilized Pickering Emulsion Templating Methodology

Using the acid-modified palygorskite-stabilized oil-in-water Pickering emulsion templating methodology, microencapsulation of ginger essential oil was prepared exploiting pectin and chitosan hydrochloride. To improve efficiency of microencapsulation, the process of preparation was optimized by response surface methodology and a three-level and three-variable Box–Behnken design. Results showed that optimal preparation of Pickering emulsion was observed at acid-modified palygorskite concentration of 1.0%, oil phase volume fraction of 10%, and an aqueous phase pH of 7.5. The optimal preparation process of ginger essential oil microcapsules was as follows: water-bath temperature 55°C, water-bath time 3 h, ratio of core to wall 1:2, stirring speed 600 rpm, and inlet air temperature 180°C. The encapsulation efficiencies of ginger essential oil microcapsules prepared under such conditions were 94.064% ± 0.133%.

Pickering emulsion template method induced highly oriented functionalized graphene oxide in PDMS composites to achieve high gas barrier properties

Constructing oriented layered filler networks in methyl vinyl silicone rubber (PDMS) composites is an effective strategy to enhance their gas barrier properties. Herein, GO was first functionalized by sodium dodecyl benzene sulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) to form amphiphilic GO (SCGO). Furthermore, SCGO and PDMS were mixed to form the water-in-oil type SCGO/PDMS Pickering emulsions. A porous PDMS masterbatch contained hollow SCGO shells was further obtained through freeze-drying the SCGO/PDMS Pickering emulsions. Followed by hot pressing, these hollow shells composed of SCGO sheets collapsed to form the oriented filler networks in the PDMS composites. When the content of SCGO was 3 phr, the gas barrier properties of SCGO/PDMS composites increased 85.7% relative to the pure PDMS. Meanwhile, the gas barrier properties of the SCGO/PDMS composites with oriented filler networks were 20–30% higher than those of the SCGO/PDMS composites with random filler networks at the same filler content.

Stretchable, rapid self-healing guar gum-poly(acrylic acid) hydrogels as wearable strain sensors for human motion detection based on Janus graphene oxide

Wearable strain sensors have received widespread attention in research fields due to their applications in human motion detection. In this manuscript, the fabrication of functionalized Janus graphene oxide (GO) nanosheets were used by Pickering emulsion template. Polypyrrole (PPy) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) were asymmetrically grafted on the two sides of GO (GO@PPy/PDMAEMA Janus NS), which successfully applied to synthesize Janus NS/guar gum-poly(acrylic acid) (GG-PAA) self-healing nanocomposite hydrogels. The outstandingly improved self-healing efficiency (92.8% for 2 h) and mechanical properties (strength of 4.12 MPa and toughness of 873.8%) of nanocomposite hydrogels were mainly supported by the collaborative effect of reversible electrostatic interactions, multiple hydrogen bonds and metal-ligand coordination. Moreover, the hydrogels exhibited strain sensitivity and could be able to monitor a variety of human motions, which have outstanding application prospects in wearable flexible sensors.

Fluorine-Free Superhydrophobic Coating with Antibiofilm Properties Based on Pickering Emulsion Templating.

This study presents antibiofilm coating formulations based on Pickering emulsion templating. The coating contains no bioactive material because its antibiofilm properties stem from passive mechanisms that derive solely from the superhydrophobic nature of the coating. Moreover, unlike most of the superhydrophobic formulations, our system is fluorine-free, thus making the method eminently suitable for food and medical applications. The coating formulation is based on water in toluene or xylene emulsions that are stabilized using commercial hydrophobic silica, with polydimethylsiloxane (PDMS) dissolved in toluene or xylene. The structure of the emulsions and their stability was characterized by confocal microscopy and cryogenic-scanning electron microscopy (cryo-SEM). The most stable emulsions are applied on polypropylene (PP) surfaces and dried in an oven to form PDMS/silica coatings in a process called emulsion templating. The structure of the resulting coatings was investigated by atomic force microscopy (AFM) and SEM. The surface of the coatings shows a honeycomb-like structure that exhibits a combination of micron-scale and nanoscale roughness, which endows it with its superhydrophobic properties. After tuning, the superhydrophobic properties of the coatings demonstrated highly efficient passive antibiofilm activity. In vitro antibiofilm trials with E. coli indicate that the coatings reduced the biofilm accumulation by 83% in the xylene-water-based surfaces and by 59% in the case of toluene-water-based surfaces.

Pickering emulsion strategy to control surface wettability of polymer microspheres for oil–water separation

Surface wettability, one of the most important parameters for oil–water separation, depends on the chemical composition and surface roughness of a material. Herein, the Pickering emulsion template method is proposed to control the surface wettability of polymer microspheres. Upon the dispersion of modified diatomite particles in the aqueous phase, a superhydrophobic surface was formed on the polymer microspheres via Pickering emulsion polymerization, with a water contact angle of 152°. When the initial dispersion location of the modified diatomite particles changed from water to oil, a hydrophilic/underwater superoleophilic surface with micro/nanoscale hierarchical structures formed on the polymer microspheres. This special wettability enabled the microsphere layer to serve as an adsorbent with underwater superoleophilicity, achieving efficient oil separation from various oil-in-water emulsions with high separation efficiency of >99.8%. Hence, this study provides a valuable strategy based on the Pickering emulsion template method to design materials with special wettability for realizing promising emulsion separation.

Lightweight, strong, and form-stable cellulose nanofibrils phase change aerogel with high latent heat

Phase change material (PCM) is promising for energy storage and release. However, the deformation and leaking during phase change generally limit its application. Herein, a lightweight, strong, and form-stable PCM aerogel was fabricated using Pickering emulsion templating technique. Cellulose nanofibrils (CNFs) were used to stabilize PCM into Pickering emulsion, which was further integrated into a 3D interconnected CNF network forming CNF/PCM composite aerogel. The composite aerogel is strong that can support over 5000 times of its own weight, and demonstrates exceptional form stability at 80 °C, showing no leakage after 20 heating/cooling cycles. The latent heat of CNF/PCM composite aerogel could reach 173.59 J·g−1, approximately 84.4% of the paraffin. The CNF/PCM composite aerogel showed relatively low thermal conductivity of 32.0–37.7 mW·m−1·K−1. The sustainability and impressive thermal regulating properties of the CNF/PCM composite aerogel make it an ideal candidate for applications in smart textile, smart building, batteries, and electronic devices.

Fabrication of chitin nanofiber-PDMS composite aerogels from Pickering emulsion templates with potential application in hydrophobic organic contaminant removal

Natural polymers have aroused increasing attention in water treatment but their application in removing hydrophobic organic contaminants (HOCs) was limited due to their hydrophilicity. Herein, hydrophobic aerogels were successfully fabricated from Pickering emulsions stabilized by chitin nanofibers (ChNF) with polydimethylsiloxane (PDMS) as dispersed phase and glutaraldehyde as a crosslinking agent, and their performance in HOCs removal were evaluated. The Pickering emulsions with PDMS ratios of 2.5–20% v/v showed high stability, demonstrating great potential as aerogel templates. The solidified PDMS droplets were evenly distributed within the matrix, contributing to homogeneous and permanent hydrophobicity. The composite aerogels with water contact angles of over 130° could selectively remove non-aqueous phase HOCs from water. The CCl4 adsorption capacity was 521–2820 wt%, depending on PDMS contents. Meanwhile, the mechanical resilience of the composite aerogels was significantly improved, facilitating the adsorbent regeneration by simple mechanical squeezing. The adsorption capacity remained above 85% for 24 cycles. Moreover, the aerogels could also remove dissolved HOCs from water with a maximum adsorption capacity of 1.34 mg/g for 10 mg/L TCE. This work reveals the potential of Pickering emulsions in the fabrication of composite hydrophobic materials from natural biopolymers with promising application in HOCs related water treatment.

Fabrication of self-healing nanocomposite hydrogels with the cellulose nanocrystals-based Janus hybrid nanomaterials

Janus nanomaterials possess remarkable prospects in the design of a series of smart materials with unique asymmetric properties. In this work, surface functionalized Janus cellulose nanocrystalline-type (CNCs-type) nanomaterials were manufactured by Pickering emulsion template and the construction of self-healing nanocomposite hydrogels has been realized. During emulsification, the mussel-inspired chemistry was employed to develop Janus nanocomposites. The extension of molecular chain of poly-lysine (PLL) and the polydopamine (PDA) coating were grafted on different sides of CNCs. Afterwards, the prepared nanocomposites were added to poly (acrylic acid) (PAA)-based hydrogels which formed by in-situ polymerization. The collaborative effect of metal-ligand coordination between the molecular chain of PLL, PDA coating, PAA chains and metal ions endowed the nanocomposite hydrogels with excellent mechanical properties (8.8 MPa) and self-healing efficiency (88.9%). Therefore, the synthesized Janus CNCs-PDA/PLL nanocomposites are expected to have diverse application in the development of smart materials with self-healing ability.

Fabrication and antibacterial evaluation of peppermint oil-loaded composite microcapsules by chitosan-decorated silica nanoparticles stabilized Pickering emulsion templating

Novel peppermint oil (PO)-loaded composite microcapsules (CM) with hydroxypropyl methyl cellulose (HPMC)/chitosan/silica shells were effectively fabricated by PO Pickering emulsion, which were stabilized with chitosan-decorated silica nanoparticles (CSN). The surface modification of chitosan could improve the hydrophobicity of silica nanoparticles and favor their adsorption at the oil-water interface of PO Pickering emulsions. The microcapsule composite shells were formed dependent on the electrostatic adsorption of HPMC and CSN, and further subjected to spray-drying. The peppermint oil-loaded composite microcapsules with 100% HPMC as wall material (PO-CM@100%HPMC) seemed to be optimum formulation based on the prolonged release, acceptable entrapment efficiency (89.1%) and drug loading (25.5%). The PO-CM@100%HPMC could remarkably prolong the stability of PO. Moreover, the PO-CM@100%HPMC had a long-term antimicrobial activity (85.4%) against S. aureus and E. coli even after storage for 60 days. Therefore, the Pickering emulsions based microcapsules seemed to be a promising strategy for antibacterial application for PO.

From wastes to interconnected porous monolith: Upcycling of Al-based metal organic framework via pickering emulsion template

An Al-based Metal-Organic Framework (MOF) obtained from Li-ion battery wastes as an upcycled material has been shaped as a hierarchically porous solid monolith. This original method is based on the stabilization of a Pickering High Internal Phase Emulsion (HIPE) by MOF particles that conducts to the formation of a monolith after polymerization of the aqueous continuous phase and elimination of the organic internal phase of the emulsion. The presence of a small amount of additive polymers rigidifies the monolith structure and an adhesive binder is used to improve the final network porosity of the materials by creating pore throats. This makes the MOFs accessible at the internal surface of the monolith after shaping and keeps some of their original properties. A screening of the different parameters is proposed to optimize the ratio MOF/Polymer/Adhesive binder and retains at best the original properties of the MOFs. This work shows the great ability of MOFs to stabilize Pickering emulsions and to conduct to a solid polymer-MOF composite monolith with interesting properties. We assume that this method can be generalized to other MOFs materials.

Stable sunflower oil oleogel from oil/water pickering emulsion with regenerated chitin

Pickering emulsion templating is a versatile technique in formulating highly networked oil-in-water emulsions applicable in foods, cosmetics, and pharmaceuticals areas. In this work, oleogels was prepared by oil-in-water Pickering emulsions using regenerated chitin (RCh) as the stabilizing particles. The effects of RCh concentrations (0.4/100–1.4 g/100 g) on the formation, rheology, and log-term stability of the emulsions and oleogles were investigated. It was found that the solid-like oloegel with a high concentration of liquid oil (≥98 g/100 g) could be obtained after evaporating of water from the emulsions. Shear-thinning behavior was observed at lower concentrations of RCh (0.4–0.6 g/100 g) and higher frequencies in the emulsions. An increase in the viscoelastic property was achieved. Oleogels containing higher concentrations of RCh (0.8/100–1.4 g/100 g) showed excellent resistance against coalescence and Ostwald ripening during the storage time. These oleogels also showed good thermal stability (no sign of oil leakages) when heated to 80 °C for 2 days. This emulsion templating approach is a feasible oil structuring strategy promising to be used in various applications.

Regenerated chitin reinforced polyhydroxybutyrate composites via Pickering emulsion template with improved rheological, thermal, and mechanical properties

Nanochitin is a promising nanofiller for the development of nanocomposites materials, whose overall performance is greatly dependent on the dispersity of the filler. Here, we employed the Pickering emulsion platform to prepare a uniformly distributed regenerated nanochitin (RCh)/polyhdroxybutyrate (PHB) composites. The produced PHB/RCh nanocomposites were studied for their thermal, mechanical, and rheological properties. It was found that the addition of 1.5% RCh markedly increased the thermal decomposition temperature by 24 °C than pure PHB. Similarly, both the storage modulus and tensile strength were also improved by 37% and 45%, respectively with regards to the neat PHB. Moreover, the rheological results also elucidated that the introduction of RCh improved the viscoelastic characteristics of the neat PHB over the frequencies range. Thus, the Pickering emulsion technique provides a simple and green method for preparing RCh-reinforced polymer nanocomposite materials used in packaging applications.

One-Step Synthesis of Solid-Liquid Composite Microsphere for CO2 Capture.

The design and development of efficient adsorbents for CO2 capture is of paramount importance. Herein, we report a novel Pickering emulsion templating strategy to prepare a hierarchically structured, micrometer-sized solid-liquid composite microsphere (SLCM) for CO2 capture. This strategy enables us to introduce liquid amine into porous silica nanospheres which are encapsulated by the hydrophobic shell of micrometer-sized sphere through a one-step synthesis. The interior architectures, microsphere sizes, and anime loading can be facilely tuned through varying the synthesis conditions. The developed SLCM exhibits excellent CO2 adsorption capacity, fast adsorption kinetics, long-term recyclability, and reduced loss of amine in industrially preferred fixed-bed reactors. Interestingly, it was found that the adsorption behavior was dependent on the interior structure of SLCM. This study opens a new way to design efficient solid-liquid composite materials.

Porous Hydroxyapatite Foams: Excellent Carrier of Hydrated Salt with Adjustable Pores for Thermal Energy Storage

Porous hydroxyapatite foam (PHF) was synthesized via a Pickering emulsion template for encapsulating disodium hydrogen phosphate dodecahydrate (DHPD). PHF consisted of open large pores connected by a window structure, and its pore size was adjusted in the range of 1.78 to 14.87 μm. The contact angle test proved that PHF owned a good adsorption to DHPD. In SEM and EDS images, the interconnected pore structure and packaging characteristics were proved. Through XRD, FT-IR, and TGA analysis, it was proved that the composite phase change material (CPCM) had well chemical stability and thermal stability. The most favorable thermal performance was shown by the sample with a pore diameter of 5.32 μm, and its phase transition temperature and phase transition enthalpy were 44.6 °C and 177.1 J/g, respectively. In addition, the latent heat only decreased by 0.83% after 100 thermal cycles, which reflected a favorable thermal reliability. Therefore, the prepared CPCM owned promising ion potentials in waste heat recovery and building energy saving.

Spontaneous Agglomeration of Fluorinated Janus Particles and Its Effect on the Adsorption Behavior of Oil-Air Surfaces.

Based on the Pickering emulsion template method, two types of Janus particles with different relative amphiphilic areas for stabilizing non-aqueous foam were synthesized. In addition, particles with uniformly modified surface were synthesized for comparison. By adjusting oil mixtures, the behavior of particles on the oil-air surface was measured. Moreover, the role of particle agglomerates in surface adsorption process was investigated. Affected by the particle surface contact angle, the surface activity of Janus particles is not always greater than that of uniformly modified particles, which is reflected on delta surface tension and the volume of foam generated. The oil-surface adsorption process of synthesized Janus particles is not only occurred in the form of independent detached particles, but also in the form of particle agglomerates. The adsorption of the particles from the bulk phase to the surface requires the contact angle of the Cassie–Baxter composite surface of the particle agglomerates to be around 90°, but the inherent contact angle of the individual particles is <90°.

Formation Mechanism of Multipurpose Silica Nanocapsules.

Core–shell structures containing active materials can be fabricated using almost infinite reactant combinations. A mechanism to describe their formation is therefore useful. In this work, nanoscale all-silica shell capsules with an aqueous core were fabricated by the HCl-catalyzed condensation of tetraethyl orthosilicate (TEOS), using Pickering emulsion templates. Pickering emulsions were fabricated using modified commercial silica (LUDOX TMA) nanoparticles as stabilizers. By following the reaction over a 24 h period, a general mechanism for their formation is suggested. The interfacial activity of the Pickering emulsifiers heavily influenced the final capsule products. Fully stable Pickering emulsion templates with interfacially active particles allowed a highly stable sub-micrometer (500–600 nm) core–shell structure to form. Unstable Pickering emulsions, i.e., where interfacially inactive silica nanoparticles do not adsorb effectively to the interface and produce only partially stable emulsion droplets, resulted in capsule diameter increasing markedly (1+ μm). Scanning electron microscope (SEM) and transmission electron microscope (TEM) measurements revealed the layered silica “colloidosome” structure: a thin yet robust inner silica shell with modified silica nanoparticles anchored to the outer interface. Varying the composition of emulsion phases also affected the size of capsule products, allowing size tuning of the capsules. Silica capsules are promising protective nanocarriers for hydrophilic active materials in applications such as heat storage, sensors, and drug delivery.

Pickering-emulsion-templated synthesis of 3D hollow graphene as an efficient oil absorbent.

The preparation of graphene in three-dimensional mode represents an alternative method to maintain its characteristically large surface area, which, under normal circumstances, is diminished by the restacking of the individual sheets. Sufficiently stable 3D graphene enables the high surface area characteristic of monoatomic graphene layers to be obtained. Based on the coupling of the high surface area and the void spaces that are thus created, which act as pores, 3D graphene is anticipated to have potential as a sorbent material. In this study, lightweight 3D hollow graphene featuring a unique thin skeletal framework was developed using the Pickering emulsion route for oil absorbent applications. In this technique, toluene droplets stabilized by graphene oxide layers in a water system were used as the template, and upon the removal of the solvent by freeze-drying and microwave-assisted reduction, 3D hollow graphene was obtained. The produced 3D graphene demonstrates excellent sorption efficiencies of 84 to 145 g g−1 for different types of oil and organic solvents in the first absorption. This excellence can be attributed to its multi-level porosity as elucidated by mercury intrusion porosimetry (MIP) and Brunauer–Emmett–Teller (BET) surface area analysis, which indicated a bimodal pore size distribution with macroporosity and mesoporosity and a surface area of 127 m2 g−1. The 3D hollow graphene prepared using the Pickering emulsion template technique incorporating microwave treatment can be readily recycled using a solvent extraction process for a total of ten sorption–desorption cycles without significant losses in its efficiency, making it promising for further consideration as an appropriate material for oil spill incidents.

Self-assembling graphene oxide/modified amphipathic hydroxyethyl cellulose hybrid stabilized Pickering emulsion polymerization for functional hydrogel

Herein, a self-assembled hybrid from bromoacetic acid (BA) modified amphipathic hydroxyethyl cellulose (MAHEC) and graphene oxide (GO) was prepared and used as Pickering emulsifiers to synthesizing functional porous hydrogel by removing the oil phase after emulsion templating polymerization. The MAHEC grafted with the 1-bromododecane was prepared by the phase-transfer method, and the graphene oxide was prepared by Hummers’ method. The interaction between the GO nanosheets and MAHEC molecular chain was investigated by X-Ray Diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The amphipathy of the GO and MAHEC was measured by the water contact angle, which was 74.0° and 103.0°, respectively. A stable, low cost, and biocompatible Pickering emulsion was fabricated by a low concentration of GO and MAHEC hybrid. Stabilization of Pickering emulsion prepared by the nanohybrid emulsifier GO and MAHEC at different conditions was investigated, such as different electrolyte concentration, pH, and oil/water ratio. The polyacrylamide (PAM) organo-hydrogel was polymerized by the stable Pickering emulsion template. After removing the olive oil, the inner wall of the porous hydrogel was coated by the MAHEC and GO for the pH-sensitive release. The strategy of Pickering emulsion templating polymerization by utilizing functional emulsifiers could be applied for the preparation of various smart materials.