Specially Treated Aramid Fiber Stabilized Gel‐Emulsions: Preparation of Porous Polymeric Monoliths and Highly Efficient Removing of Airborne HCHO

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.

High Performance Microwave Absorption of Lightweight and Porous Non-carbon-based Polymeric Monoliths via Gel Emulsion Template

A special porous non-carbon-based microwave-absorbing materials are designed and synthesized by bonding di(prop-1-en-2-yl) ferrocene into porous polymeric monoliths made by gel-emulsions as templates. In this study, a sequence of porous...

Emulsion-templated porous polymers: drying condition-dependent properties

Macroporous materials templated using high internal phase emulsions (HIPEs) are promising for various applications. To date, new strategies to create emulsion-templated porous materials and to tune their properties (especially wetting properties) are still highly required. Here, we report the fabrication of macroporous polymers from oil-in-water HIPEs, bereft of conventional monomers and crosslinking monomers, by simultaneous ring-opening polymerization and interface-catalyzed condensation, without heating or removal of oxygen. The resulting macroporous polymers showed drying condition-dependent wetting properties (e.g., hydrophilicity-oleophilicity from freezing drying, hydrophilicity-oleophobicity from vacuum drying, and amphiphobicity from heat drying), densities (from 0.019 to 0.350 g cc^-1), and compressive properties. Hydrophilic-oleophilic and amphiphobic porous polymers turned hydrophilic-oleophobic simply by heating and protonation, respectively. The hydrophilic-oleophobic porous polymers could remove a small amount of water from oil-water mixtures (including surfactant-stabilized water-in-oil emulsions) by selective absorption and could remove water-soluble dyes from oil-water mixtures. Moreover, the transition in wetting properties enabled the removal of water and dyes in a controlled manner. The feature that combines simply preparation, tunable wetting properties and densities, robust compression, high absorption capacity (rate) and controllable absorption makes the porous polymers to be excellent candidates for the removal of water and water-soluble dyes from oil-water mixtures.

Bioinspired organohydrogels with heterostructures: Fabrications, performances, and applications

Since emerging in 1960, the artificial hydrogels have garnered enormous attentions in scientific community due to their high level of similarities to biological soft tissues in both structures and properties. With the proceeding of research, the concern of hydrogels is gradually shifted from fundamental investigation to abundant functionalization. In contrast to the natural soft tissues, the current artificial hydrogels still possess relatively simple structures and unsatisfactory environmental adaptability, extremely limiting their practical applications in complex environments. Enlightened by the prominent adaptability of biological organisms, the binary cooperative complementary principle is utilized to develop bioinspired organohydrogels by combining two components with opposite but cooperative physiochemical features. The present review provides the advanced progresses of bioinspired organohydrogels with sophisticated heterogeneous networks and desirably environmental adaptabilities. We clearly summarize the synthesizing strategies in regard to both corresponding mechanisms and typical examples, including macroscopic organohydrogels, organohydrogels with binary solvent, organohydrogels with heteronetworks, and emulsion-based organohydrogels. Meanwhile, the intriguing features of the reported organohydrogels, such as temperature resistance, switchable mechanics, adaptive wettability, and opposite components compatibility, are also clearly highlighted with a short overview of their promising applications. Ultimately, the current challenges and perspectives on the future development of bioinspired organohydrogels are also discussed.

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.