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.

New Approach for Preparation of Porous Polymers with Reversible Pore Structures for a Highly Safe Smart Supercapacitor

Porous polymers have many industrial applications, but their pore structures (open or closed) are usually fixed during polymerization. In this study, polymers with reversible and controllable pore structures, namely, thermosensitive porous hydrogels with regulated volume phase transition temperature, were prepared using a Pickering high-internal-phase emulsion as the template. Upon heating, the hydrogels transformed not only in their wettability (between hydrophilicity and hydrophobicity with water contact angles of 21.8 and 100.9°) but also their pore structure (between open through-holes and closed holes with pore throat sizes of 15.58 and 0 μm, respectively) in a short time (<10 s). When the hydrogel was used as a separator in smart supercapacitors (SCs), this behavior effectively limited the path of electrolyte migration, reducing the chance of conflagration accidents. Moreover, by utilizing the highly reversible pore structures and wettability of the porous hydrogel, reversible charging and discharging were restored after the system cooled down. This work not only provides great guidance for preparing porous polymers with reversible pore structures but also paves the way for designing smart SCs with enhanced safety.

Cellulose-based, flexible polyurethane polyHIPEs with quasi-closed-cell structures and high stability for thermal insulation

Cellulose-based, closed-cell porous materials templated from emulsions are promising for thermal insulation, but their low stability imposed by physical interaction hinders the materials from real applications. Herein, we report the fabrication of cellulose-based, flexible polyurethane polyHIPEs with quasi-closed-cell structures, high stability and flexibility for thermal insulation. The polyHIPEs were prepared from cellulose-stabilized Pickering high internal phase emulsions through interfacial crosslinking using isocyanate. The resulting polyurethane polyHIPEs showed controllable external shapes, quasi-closed-cell structures, high flexibility, low density, and robust compression (without fracture even after compression to 30 % original height). The crosslinking enabled the polyHIPEs to show hydrophobicity, good stability (without breakage and dissolution observed after immersing in NaOH solution at pH 12, HCl solution at pH 1 and hot water at 100 °C, for 24 h) and decreased moisture uptake (below 1 %). The low density and quasi-closed-cell structures endowed the polyHIPEs with high thermal insulation, with thermal conductivity as low as 33.1 mW/(m K). These features make the cellulose-based, closed-cell polyHIPEs as an excellent candidate for thermal insulting.

Emulsion-based, flexible and recyclable aerogel composites for latent heat storage

Although emulsion-based, phase change material-encapsulated monolithic composites are promising for latent heat storage, their rigidity and non-recyclability imposed by the relatively dense covalent crosslinking hinder the composites from real applications. Herein, we report the fabrication of aerogel composites with flexibility and recyclability from cellulose nanocrystal-stabilized, octadecane-encapsulated Pickering emulsions solidified using physical gelation. The resulting monolithic composites exhibited controllable external shapes, and the introduction of poly(vinyl alcohol) significantly reduced the leakage of the encapsulated octadecane. The aerogel composites showed flexibility at temperature over 30 °C, and robust compressive behavior, without fracture at 70% compressive strain. The composites possessed similar heat storage (melting) temperature and heat release (crystallization) temperature to that of bulk octadecane, high heat capacity (up to 253 J^.g^-1) and high reusability, without obvious deterioration in heat capacity after 100 heating-cooling cycles. Moreover, the aerogel composites exhibited recyclability, simply by dissolving the composites in hot water to form emulsions and then by freeze drying to form aerogel composites. The flexibility and recyclability, together with robust compression, controllable external shapes, high heat capacity and good reusability, make the aerogel composites to be excellent candidates for latent heat storage.

Microphase-separated, magnetic macroporous polymers with amphiphilic swelling from emulsion templating

PolyHIPEs are promising for various applications associated with liquid uptakes. PolyHIPEs from a reactive, monomeric block copolymer can exhibit amphiphilic swelling, but such swelling usually tends to disappear upon copolymerization...

Amphiphobic polyHIPEs with pH-triggered transition to hydrophilicity–oleophobicity for the controlled removal of water from oil–water mixtures

Amphiphobic polyHIPEs with pH-triggered transition to hydrophilicity–oleophobicity were templated from high internal phase emulsions for the controlled removal of water from oil–water mixtures.

Nanofibrous, Emulsion-Templated Syndiotactic Polystyrenes with Superhydrophobicity for Oil Spill Cleanup

A series of syndiotactic polystyrene (sPS) monoliths with controllable shapes, nanofibrous structures, hierarchical pores, superhydrophobicity, high specific surface area, and high strength have been fabricated for the first time by solidifying nonaqueous high internal phase emulsions (HIPEs) through crystallization-induced gelation. The nonaqueous HIPEs were formed by dispersing glycerol in 1,2,4-trichlorobenzene stabilized by sulfonated sPS at a high temperature of 120 °C, and with sPS in the continuous phase, these HIPEs were solidified by cooling at room temperature to obtain sPS monoliths. The shapes of the sPS monoliths were controllable, and excitedly, nanofibrous structures were found at void walls, with fiber diameters ranging from 20 to 100 nm. The sPS monoliths exhibited pores in different scales: emulsion-templated voids at nearly 10 μm with pore throats ranging from 1 to 2 μm and macropores and mesopores between nanofibers, enabling the monoliths to exhibit extremely high specific surface area of up to 420 m²·g^-1. The porous sPS monoliths were robust, and they did not fail even at a compressive strain of 70%, with Young's moduli ranging from 157.7 to 2638.0 kPa. The monoliths were superhydrophobic and oleophilic, with water contact angles over 150° and with oils absorbed rapidly. The superhydrophobicity and oleophilicity enabled the porous sPS monoliths to absorb bulk oils on the water surface, underwater oils, and even oils within oil-in-water emulsions. The monoliths absorbed a large amount of organic solvents, edible oils, and fuel oils with equilibrium liquid uptakes up to 81.3, 44.4, and 41.9 g·g^-1 for chloroform, olive oil, and diesel, respectively. The liquid absorption was rapid, and the monoliths exhibited a relatively high reusability. These porous sPS monoliths were demonstrated to be a candidate for the applications of oil/water separation and/or oil spill cleanup.

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.

Highly porous, emulsion-templated, zwitterionic hydrogels: amplified and accelerated uptakes with enhanced environmental sensitivity

Highly porous, emulsion-templated, zwitterionic hydrogels exhibited amplified and accelerated uptakes, enhanced environmental sensitivity, anti-polyelectrolyte behavior, and dual-pH sensitive uptakes.

Highly Porous Poly(high internal phase emulsion) Membranes with "Open-Cell" Structure and CO2-Switchable Wettability Used for Controlled Oil/Water Separation

Polymer membranes with switchable wettability have promising applications in smart separation. Hereby, we report highly porous poly(styrene-co-N,N-(diethylamino)ethyl methacrylate) (i.e., poly(St-co-DEA)) membranes with "open-cell" structure and CO₂-switchable wettability prepared from water-in-oil (W/O) high internal phase emulsion (HIPE) templates. The open-cell porous structure facilitates fluid penetration through the membranes. The combination of CO₂-switchable functionality and porous microstructure enable the membrane with CO₂-switchable wettability from hydrophobic or superoleophilic to hydrophilic or superoleophobic through CO₂ treatment in an aqueous system. This type of membrane can be used for gravity-driven CO₂-controlled oil/water separation, in which oil selectively penetrates through the membrane and separates from water. After being treated with CO₂ switching wettability of the membrane, a reversed separation of water and oil can be achieved. Such a wettability switch is fully reversible, and the membrane could be regenerated through simple removal of CO₂ and oil residual through drying. This facile and cost-effective approach represents the development of the first CO₂-switchable polyHIPE system, which is promising for smart separation in a large volume.

A soluble star-shaped silsesquioxane-cored polymer—towards novel stabilization of pH-dependent high internal phase emulsions

A well-defined pH-responsive star-shaped polymer containing poly(N,N-dimethylaminoethyl methacrylate) (PDMA) arms and a cage-like methacryloxypropyl silsesquioxane (CMSQ-T₁₀) core was used as an interfacial stabilizer for emulsions consisting of m-xylene and water.