Antagonistic effect of particles and surfactant on pore structure of macroporous materials based on high internal phase emulsion

Transparent Oil-Water Separating Hydrophobic Sponge Prepared from a Pickering High Internal Phase Emulsion Stabilized by Octadecyltrichlorosilane Grafting Carbon Nanotubes

Increasingly, oil spills and industrial discharges are wreaking havoc on the water environment; in order to efficiently separate oil and water from sewage containing oil or organic solvents, a novel porous polymer (P(EHA-co-BA)) was prepared by Pickering high internal phase emulsion (HIPE) template method. To obtain polyHIPE with better oil/water separation capacities, octadecyltrichlorosilane (OTS)-modified carbon nanotubes (CNTs) and surfactants were used as costabilizers for HIPE, which improved the stability of HIPE as well as the mechanical properties and the separation efficiency of polyHIPE. In the presence of 1 wt % OTS-CNT adding in the oil phase, 1%OTS-CNT polyHIPE has high porosity (92.21%), favorable hydrophobicity (a water contact angle of 128°), and excellent mechanical properties. As a result, 1%OTS-CNT polyHIPE has high absorption of oils and oily solvents, e.g., dichloromethane up to 36 g/g, and maintains an absorption efficiency of >97% after 20 reapplications. In the formulation of polyHIPE, cinnamaldehyde (CA) has been added to provide superior antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). It appears that the novel polyHIPE proposed in this work is a reusable antibacterial porous polymer with promising applications for oil-water separation.

Hyperbranched Polyethylenimine-Tethered Multiple Emulsion-Templated Hierarchically Macroporous Poly(acrylic acid)-Al2O3 Nanocomposite Beads for Water Purification

Emulsion template-guided strategy has been used to produce porous architectures with exquisite structure, tailored morphology, and exclusive features for ubiquitous applications. Notwithstanding, the practical water remediation is often marred by their transport-limited behavior and fragility. To circumvent these conundrums, we prepared hierarchically porous poly(acrylic acid)-alumina nanocomposite beads by solidifying the droplets of emulsions jointly stabilized by the organic surfactants and alumina nanoparticles. By virtue of their positive charge, the alumina nanoparticles got entrapped within the poly(acrylic acid) scaffolds that excluded the risk of secondary contamination typically observed with conventional nanocomposites. Being amenable to surface modification, the carboxyl moieties of the beaded polymer were further exploited to covalently tether branched polyethylenimine throughout the exterior and interior surface of the porous matrix via a grafting-to approach. The macropores expedite an active fluid flow and easier adsorbate transport throughout the functionalized nanocomposites whose overall higher density of positive charge over a certain pH range electrostatically attracts and effectively adsorbs the negatively charged Cr(VI) complexes and anionic congo red ions/molecules from water. This proof-of-concept synthetic approach and postsynthetic modification offer an improved mechanical robustness to these macrosized multifunctional nanocomposite beads for their easier processing, thereby paving the way for the point-of-use water purification technology development.

High Internal Phase Emulsions Synergistically Stabilized by Sodium Carboxymethyl Cellulose and Palm Kernel Oil Ethoxylates as an Essential Oil Delivery System

High internal phase emulsions (HIPEs) with an internal phase fraction of 84 vol % were prepared using carboxymethyl cellulose (CMC) and palm kernel oil ethoxylates (SOE-N-60) as a dual emulsifier. Effects of the oil-phase volume fraction, CMC concentration, and SOE-N-60 concentration on oil-in-water HIPEs stability were systematically studied by a Mastersizer 2000 instrument, Lx POL polarizing microscope, rheometer, etc. The bioavailability of tea tree oil can be effectively protected using HIPEs as a delivery system. The experimental results showed that, with the increase of the concentrations of CMC and SOE-N-60, the droplet size of HIPEs gradually decreases and the HIPEs showed good static stability. In addition, it was observed by scanning electron microscopy that the polyHIPEs materials using HIPEs stabilized by different SOE-N-60 and CMC concentrations as templates had different structures. Moreover, the synergism between CMC and SOE-N-60 surfactants plays a significant role in the preparation and stability of HIPEs.

Polydimethylsiloxane nanocomposite macroporous films prepared via Pickering high internal phase emulsions as effective dielectrics for enhancing the performance of triboelectric nanogenerators

Polydimethylsiloxane (PDMS) nanocomposite (NC) macroporous films were prepared by a Pickering high internal phase emulsion (HIPE) templating technique and used as effective dielectrics for enhancing the performance of triboelectric-nanogenerators (TENGs). HIPEs were formulated using commercial PDMS and water as the continuous and dispersed phase, respectively. The formation and solidification of PDMS-based HIPEs were possible through stabilization with silver-nanoparticles (Ag-Nps) and surfactant (Span 20) mixtures. The resulting PDMS-NC-polyHIPE films presented an interconnected 3D macroporous structure with Ag-Nps on their porous surface. The addition of different amounts of Ag-Nps (0, 4, 20, 28, 36 wt%) in HIPE formulations allowed modification of the pore size, total pore volume and dielectric properties of the tribo-materials. Results revealed that both the porosity and dielectric properties of these materials play an important role in enhancing the output performance of TENGs. Thus, the best TENG based on the PDMS-NC-polyHIPE film was achieved with 20 wt% of Ag-Nps, with voltage, current and power values of 4.88 V, 0.433 μA and 2.1 μW, respectively, which gives over 3.28-fold power enhancement compared with the reference TENG (based on a PDMS film without porosity or Ag-Nps). Therefore, the preparation of tribo-materials through a Pickering HIPE templating technique provides a novel, effective and easy way for the improvement of the TENG's performance.

Recent advances in separation applications of polymerized high internal phase emulsions

Polymerized high internal phase emulsions as highly porous adsorption materials have received increasing attention and wide applications in separation science in recent years due to their remarkable merits such as highly interconnected porosity, high permeability, good thermal and chemical stability, and tailorable chemistry. In this review, we attempt to introduce some strategies to utilize polymerized high internal phase emulsions for separation science, and highlight the recent advances made in the applications of polymerized high internal phase emulsions for diverse separation of small organic molecules, carbon dioxide, metal ions, proteins, and other interesting targets. Potential challenges and future perspectives for polymerized high internal phase emulsion research in the field of separation science are also speculated at the end of this review.

Preparation of porous adsorbent via Pickering emulsion template for water treatment: A review

Porous materials as emerging potential adsorbents have received much more attention because they are capable of capturing various pollutants with fast adsorption rate, high adsorption capacity, good selectivity and excellent reusability. In order to prepare porous materials with decent porous structure, Pickering emulsion template method has been proved to be one of the most effective technologies to create pore structure. This paper reviewed comprehensively the latest research progress on the preparation of porous materials from various Pickering emulsions and their applications in the decontamination of pollutants (e.g., heavy metal ions, organic pollutants) and in the oil/water separation. It was expected that the summaries and discussions in this review will provide insights into the design and fabrication of new efficient porous adsorbents, and also give us a better understanding of the subject.

Enhancing the Viability of Lactobacillus plantarum as Probiotics through Encapsulation with High Internal Phase Emulsions Stabilized with Whey Protein Isolate Microgels

Probiotics with positive physiological effects on intestinal microflora populations of the host are popular in functional foods. Low relative humidity (RH) and temperature are beneficial for probiotic survival. In the present study, freeze-dried Lactobacillus plantarum powder, representative of probiotics, was encapsulated in the high internal phase emulsions (HIPEs) stabilized with whey protein isolate (WPI) microgels, to avoid the contact of water. Homogeneously dispersed WPI microgels with particle sizes around 300 nm were formed through thermal treatment of WPI solution. The particle size of the microgels decreased with the elevation of protein concentrations as well as the departure of pH values from the isoelectric point of the protein. When internal oil phase volume fractions were higher than 80% (w/w), WPI microgels with concentrations higher than 4.0 wt %, prepared at pH 4.0, 6.0, and 7.0 conditions, could stabilize the oil to form homogeneous HIPEs with tilting stability. The HIPEs thus formed had a cellular and tunable pore structure that could resist mechanical perturbation. Encapsulation of L. plantarum within HIPEs successfully increased the cell viability after pasteurization processing. The protective effect was even improved with the elevation of the oil volume fraction and increase of WPI microgel concentrations. Under different pH conditions, the strongest protective effect appeared at pH 4.0, when the WPI microgels accumulated on the oil droplet surface. When the large amount of oil and the protein microgel layer on the oil-water interface were combined as two specialties, the HIPEs were demonstrated to have high potential for enhancing the viability of probiotics during food thermal processing.

Methyl Methacrylate HIPE Solely Stabilized by Fluorinated Di-block Copolymer for Fabrication of Highly Porous and Interconnected Polymer Monoliths

Preparation of stable water-in-oil (W/O) high internal phase emulsion (HIPE) containing methyl methacrylate (MMA) monomer as oil phase is a difficult task due to the significant solubility of MMA in water. Here, for the first time a fluorinated di-block copolymer (FDBC) poly (2-dimethylamino)ethylmethacrylate-b-poly (trifluoroethyl methacrylate) (PDMAEMA-b-PTFEMA) is proposed to stabilize HIPEs of MMA without the use of any co-stabilizer or thickening agent. Fluorinated segments in FDBC anchored well at oil/water interface of HIPE, offering high hydrophobicity to the partially hydrophilic MMA monomer and in turn stabilization to MMA-HIPE. By using fluorinated di-block copolymer as stabilizer, highly stable HIPEs can be obtained. In addition, highly interconnected porous monoliths were obtained after free radical polymerization, which are highly desirable materials in various practical applications including tissue engineering scaffolds, separation science, bio-engineering and so on. The as-prepared MMA-HIPEs possess high thermal stability without phase separation. The textural characteristics of as-prepared composites, such as pore size and distribution, can be easily controlled by simply varying the amount of FDBC and/or dispersed phase fraction. Moreover, the influence of di-block concentration on water uptake (WU) capability of the prepared porous monoliths is explored.

Closed-cell, emulsion-templated hydrogels for latent heat storage applications

Hydrogel polyHIPEs with closed-cell structures were prepared from o/w Pickering HIPEs, and applied in latent heat storage.

Polymerized high internal phase emulsion monolithic material: a novel stationary phase of thin layer chromatography

PolyHIPE monolith plate with macroporous structure was prepared and employed for thin layer chromatograph to identify ingredients successfully.