A simple and environment-friendly approach for synthesizing macroporous polymers from aqueous foams

Emulsion-Templated Gelatin/Amino Acids/Chitosan Macroporous Hydrogels with Adjustable Internal Dimensions for Three-Dimensional Stem Cell Culture

The demand for macroporous hydrogel scaffolds with interconnected porous and open-pore structures is crucial for advancing research and development in cell culture and tissue regeneration. Existing techniques for creating 3D porous materials and controlling their porosity are currently constrained. This study introduces a novel approach for producing highly interconnected aspartic acid-gelatin macroporous hydrogels (MHs) with precisely defined open pore structures using a one-step emulsification polymerization method with surface-modified silica nanoparticles as Pickering stabilizers. Macroporous hydrogels offer adjustable pore size and pore throat size within the ranges of 50 to 130 μm and 15 to 27 μm, respectively, achieved through variations in oil-in-water ratio and solid content. The pore wall thickness of the macroporous hydrogel can be as thin as 3.37 μm and as thick as 6.7 μm. In addition, the storage modulus of the macroporous hydrogels can be as high as 7250 Pa, and it maintains an intact rate of more than 92% after being soaked in PBS for 60 days, which is also good performance for use as a biomedical scaffold material. These hydrogels supported the proliferation of human dental pulp stem cells (hDPSCs) over a 30 day incubation period, stretching the cell morphology and demonstrating excellent biocompatibility and cell adhesion. The combination of these desirable attributes makes them highly promising for applications in stem cell culture and tissue regeneration, underscoring their potential significance in advancing these fields.

Liquid foams: Properties, structures, prevailing phenomena and their applications in chemical/biochemical processes

Liquid foams are gas-liquid dispersions with flexible structures that provide high gas-liquid interfaces. This property nominates liquid foams as excellent gas-liquid contactors, systems that are widely used in the chemical and biochemical industries. However, challenges such as a lack of comprehensive understanding and foam instability have historically hindered their widespread industrial use in most applications. It was not until the recent development of nanofluidics, nanotechnology, surface science, and other related fields that the understanding, analysis, and control of foam phenomena improved. This led to the development of innovative stabilization techniques and foam-based unit operations in chemical and biochemical processes, each of which requires in-depth and exclusive reviews to fully comprehend their potential and limitations and to identify areas for further improvement and innovation. This paper reviews the foams, the common phenomena in them, the characteristics that make them suitable for chemical/biochemical engineering, reports on their current applications and recent developments in this field.

Porous superabsorbent composites prepared from aqueous foam template and application evaluation

Rapid water absorption is very important for the application of superabsorbent polymers under dry or semi-dry conditions, but there are currently few relevant studies. In this context, a novel porous superabsorbent of chitosan-grafted acrylic copolymer-2-acrylamido-2-methylpropanesulfonic acid/sapindus mukorossi pericarp/calcined oil shale semi-coke (CS-g-P(AA-co-AMPS)/SMP/COSSC) was prepared by a green and convenient foam template method, which was triggered by redox polymerization. The rich pore structure of the porous superabsorbent was conducive to accelerating the water absorption rate. It only took 15 min to reach a swelling capacity of 650 g g-1 in distilled water. Soil experiments show that even with the addition of 0.5 wt% porous superabsorbent, the soil water retention time can be extended to 7 days. Finally, it was applied to the growth of cabbage seeds and it was found that the growth was significantly improved. Based on these excellent properties, we expect to provide a valuable reference for the preparation of fast-absorbing materials through the green water-based foam template method, contributing to sustainable agriculture.

Liquid Fraction Effect on Foam Flow through a Local Obstacle

An experimental study of quasi-two-dimensional liquid foams with varying liquid fractions is presented. Experiments are conducted in a Hele-Shaw cell with a local permeable obstacle placed in the center and filling 35, 60 and 78% of the cell gap. Foam velocity is calculated using a standard cross-correlation algorithm. Estimations of the liquid fraction of the foam are performed using a new simplified method based on a statistical analysis of foam cell structures. The pattern of the foam velocity field varies with increasing liquid fraction, responsible for significant variation of the foam's rheology. The local permeability decreases with increasing obstacle height and liquid fraction. In case of high liquid fraction (5.8×10-2), the permeability coefficient tends to zero for obstacles filling more than 78% of the cell gap.

Hydrogel foams from liquid foam templates: Properties and optimisation

Hydrogel foams are an important sub-class of macroporous hydrogels. They are commonly obtained by integrating closely-packed gas bubbles of 10-1000 μm into a continuous hydrogel network, leading to gas volume fractions of more than 70% in the wet state and close to 100% in the dried state. The resulting wet or dried three-dimensional architectures provide hydrogel foams with a wide range of useful properties, including very low densities, excellent absorption properties, a large surface-to-volume ratio or tuneable mechanical properties. At the same time, the hydrogel may provide biodegradability, bioabsorption, antifungal or antibacterial activity, or controlled drug delivery. The combination of these properties are increasingly exploited for a wide range of applications, including the biomedical, cosmetic or food sector. The successful formulation of a hydrogel foam from an initially liquid foam template raises many challenging scientific and technical questions at the interface of hydrogel and foam research. Goal of this review is to provide an overview of the key notions which need to be mastered and of the state of the art of this rapidly evolving field at the interface between chemistry and physics.

Removal of antibiotics from aqueous solution by using porous adsorbent templated from eco-friendly Pickering aqueous foams

The aqueous foam template without any solvent and only using the particles stabilizer has attracted much attention for preparation of the porous adsorbents. Herein, a novel porous adsorbent was fabricated via thermal-initiated polymerization of Pickering aqueous foams, which was stabilized by the natural sepiolite (Sep) and pine pollen, and utilized for the removal of antibiotic from aqueous solution. The stabilizing mechanism of Pickering aqueous foam of that the Sep was modified with the leaching substance from pine pollen and arranged orderly around the bubble to form a dense "shell" structure was revealed. The adsorbents possessed the hierarchical porous structure and excellent adsorption performance for antibiotic of chlorotetracycline hydrochloride (CTC) and tetracycline hydrochloride (TC). The equilibrium adsorption capacities of CTC and TC were achieved with 465.59 and 330.59 mg/g within 60 min at 25°C, respectively. The adsorption process obeyed Langmuir model and pseudo-second-order adsorption kinetic model. This work provided eco-friendly approach for fabricate porous adsorbents for wastewater treatment.

Superhydrophobic metal organic framework doped polycarbonate porous monolith for efficient selective removal oil from water

A series of superhydrophobic polycarbonate porous monoliths modified with metal organic framework (Z8/PC) were firstly fabricated through a facile thermally impacted non-solvent induced phase separation method for efficient selective oil/water separation. The performance of the monoliths on oil/water separation was evaluated in terms of selectivity, equilibrium adsorption capacity, corrosion resistance, kinetics, and circulation. The results showed that the use of ZIF-8 significantly compensated for the shortage of pure monolith. Compared with pure PC monolith, the hydrophobic angle of the Z8/PC-2 monolith promoted from 136.18° to 154.25° due to the micro-nano flower surface. Meanwhile, the Z8/PC-2 monolith displayed a more intricate and continuous interconnected 3D hierarchical micro-nano structure, which possessed the monolith a higher specific surface area of 146.84 m² g^-1 and porosity of 89.5%. What's more, more superior oil/water separation abilities of Z8/PC-2 monolith were manifested by the selective removal of oil or organic solvent from water within 30s, high equilibrium adsorption capacity, and excellent corrosion resistance. In addition, the ten-cycle regeneration of porous monoliths via centrifugation or evaporation displayed additional attractiveness. Therefore, porous Z8/PC monolith will be a promising candidate for the efficient selective oil/water separation of oil spills and organic solvents.

Fabrication porous adsorbents templated from modified sepiolite-stabilized aqueous foams for high-efficient removal of cationic dyes

High internal phase emulsions (HIPEs) as template for fabrication of porous materials has attracted much attention, due to the high porosity and tunable porous structure. But the enormous consumption of organic solvents is still a nightmare for the practical application. In comparison, the aqueous foam without need any organic solvent and hence has greater advantages in the porous materials preparation. In this study, a novel Pickering foam which was stabilized by modified sepiolite (Sep) was prepared and applied as the template for preparation of the porous material via thermal-initiated polymerization. The Pickering foam had excellent ability and stability in the pH of 4-11 and the obtained porous adsorbent possess sufficient and tuned pore structure. The porous materials as adsorbent has favorable performance for adsorption and selective removal of cationic dyes, and the understanding adsorption capacities for Methylene blue (MB) and Methyl green (MG) can be achieved with 1421.18 mg/g and 638.81 mg/g within 60 and 45 min at 25 °C, respectively. This porous material can be as the potential adsorbent for adsorption or separation of organic pollutants.

Eco-friendly floatable foam hydrogel for the adsorption of heavy metal ions and use of the generated waste for the catalytic reduction of organic dyes

Benefiting from their three-dimensional network structure and various functional groups, hydrogels have emerged as efficient adsorbents for the removal of heavy metal ions from wastewater. However, the obvious drawbacks of hydrogels such as generation of toxic secondary waste after adsorption and difficulty in their separation and collection limit their practical application in wastewater treatment. Herein, we introduced a facile strategy of combining mechanical frothing and in situ radical polymerization to prepare a floatable porous foam hydrogel, which not only efficiently removed Cu2+ from water, but also could be easily collected. After adsorption, to avoid the generation of secondary toxic waste, a sustainable strategy of turning the waste into useful materials was introduced. The waste of the Cu2+_ adsorbed hydrogel was processed using NaBH4 solution to obtain a Cu nanoparticle (Cu NP)-loaded composite hydrogel, which was further employed as a catalyst for the catalytic reduction of organic dyes. Thus, this work established a convenient and sustainable strategy for the preparation of an eco-friendly floatable foam hydrogel for the efficient removal of heavy metal ions such as Cu2+ from water and turning the generated waste into useful materials, which is a concept envisaged to be applicable to other heavy metal ion-adsorbed hydrogel systems and will efficiently avoid unwanted secondary pollution.

Recent practical researches in the development of gluten-free breads

Wheat bread is consumed globally and has played a critical role in the story of civilization since the development of agriculture. While the aroma and flavor of this staple food continue to delight and satisfy most people, some individuals have a specific allergy to wheat or a genetic disposition to celiac disease. To improve the quality of life of these patients from a dietary standpoint, food-processing researchers have been seeking to develop high-quality gluten-free bread. As the quality of wheat breads depends largely on the viscoelastic properties of gluten, various ingredients have been employed to simulate its effects, such as hydrocolloids, transglutaminase, and proteases. Recent attempts have included the use of redox regulation as well as particle-stabilized foam. In this short review, we introduce the ongoing advancements in the development of gluten-free bread, by our laboratory as well as others, focusing mainly on rice-based breads. The social and scientific contexts of these efforts are also mentioned.

Overview on the use of surfactants for the preparation of porous carbon materials by the sol-gel method: applications in energy systems

Porous carbon materials attract great interest because of the wide range of applications in electrochemical energy systems, especially in the case of structured and porosity-tuned carbons prepared by template-assisted methods. The use of surfactant prevents the collapse of the porous structure during the air-drying stage in the sol-gel process, which is regarded as a critical stage in this method. This work offers an overview on the use of surfactants as templates for the manufacture of tunable porous carbon materials by the sol-gel method mainly using the polymerization reaction of resorcinol (R) and formaldehyde (F). The use of surfactants avoids the application of other economically disadvantaged drying techniques such as supercritical fluids and freeze-drying. The surfactant-assisted sol-gel methods reported in the literature for the fabrication of porous carbons are widely discussed, as well as the potentiality of the synthesized materials as electrodes in electrochemical systems, which greatly depends on the final porous structure. Besides, this work offers information on hybrid methods in which surfactants are used not only for the fabrication of porous carbon materials with mesoporous/microporous structure but also for the development of advanced structures and composites, including nanomaterials with enhanced properties. Finally, future prospects in the synthesis of carbon materials prepared by surfactant-assisted sol-gel method are presented.

Distinctive Performance of Gemini Surfactant in the Preparation of Hierarchically Porous Carbons via High-Internal-Phase Emulsion Template

The superior capability of gemini surfactant (GS) in the preparation of hierarchically porous carbons via high-internal-phase emulsion (HIPE) template followed by pyrolysis was confirmed in this work. Polymerized HIPEs (polyHIPEs) of phenol-formaldehyde resin were prepared by cross-linking the continuous phase of HIPEs stabilized by GS. Nonionic surfactant and cationic surfactant were also selected to stabilize HIPE for comparison. From scanning electron microscope observations, polyHIPEs with open-cell pore architectures were obtained with GS as emulsifier (polyHIPEs-GS) and the derived carbon foams (carboHIPEs-GS) well retained the original pore architectures, whereas polyHIPEs obtained using contrastive surfactants showed closed-cell porous structures and notable differences were observed for the derived carboHIPEs. Nitrogen adsorption/desorption measurements indicated that polyHIPEs-GS and carboHIPEs-GS both exhibited hierarchically porous architectures with much higher surface areas (SA) than those of the corresponding contrast samples. Mercury intrusion porosimetry results indicated that carboHIPEs-GS possessed higher SA and higher porosity than that of the contrast samples. The open-cell pore architecture and high SA are favorable to many applications, like energy storage. carboHIPE-GS expectably showed a higher capacitance than that of contrast samples when used as the electrode material of supercapacitor.