While emulsion-templated porous polymers (polyHIPEs) with pH-controlled wetting behaviours are advantageous for the removal of oils from oil–water mixtures, they are easily clogged by oils and are not suitable for separating mixtures consisting of a small amount of water and a large amount of oils. Herein, we report the fabrication of amphiphobic polyHIPEs from high internal phase emulsions via simultaneous solution polymerization and interface-induced polymerization. After pH adjustment with an HCl solution, the amphiphobicity of the polyHIPEs was transformed into hydrophilicity–oleophobicity, which enabled water to be selectively absorbed and separated from oil–water mixtures, and the pH-triggered transition achieved the separation in a controlled manner. Moreover, the absorption was realized in a continuous manner under an external pressure provided by a pump. The resulting hydrophilic–oleophobic polyHIPEs also absorbed water from emulsified oil–water mixtures (emulsions). The pH-triggered transition from amphiphobicity to hydrophilicity–oleophobicity and the selective absorption of water from oil–water mixtures in a continuous manner make the polyHIPEs excellent candidates for the controlled removal of water from oil–water mixtures.
High internal phase emulsions (HIPEs) are commonly stabilized by a large amount of surfactants that should be removed after the polymerization of the continuous phase, and the resulting polyHIPEs from W/O HIPEs are usually brittle and chalky. Herein we report on an amphiphilic polymerizable polyurethane (PPU) macromolecular surfactant synthesized by polyaddition reaction of diisocyanates and polyols, which can well stabilize up to 88% internal phase volume of W/O HIPE with a content of only 5 wt% based the oil phase. Compared with the HIPEs stabilized by traditional surfactant Span 80, HIPEs stabilized by PPU at either room temperature or 70 °C are much more stable owing to the increased viscosity which can inhibit droplet coalescence. Moreover, the resulting polyHIPEs not only have several times higher mechanical properties than those stabilized by Span 80 but also have higher elasticity. The effects of concentration of PPU on the morphology and mechanical properties of the resulting polyHIPEs were investigated. It was found that with the increase of PPU content, the average void and window sizes decreased, while the compression strength increased. Cyclic compression tests were performed to examine reversible compressibility and durability of these polyHIPEs. Graphical abstract The polymerizable polyurethane macromolecular surfactant (PPU) synthesized through the polyaddition reaction of diisocyanates and polyols can solely stabilize high internal phase emulsions (HIPEs), and highly interconnected macroporous polymer produced by the polymerization of HIPE stabilized with PPU, known as polyHIPE, can withstand large deformation compression with no visible cracks.
Yin Xuchu,Wang Yuting,Xu Zhiguang,Zhang Tao,Zhao Yan
Cellulose-based, porous materials (polyHIPEs) templated from emulsions are promising for thermal insulation, but their high susceptibility to combustion when exposed to fire hinders the materials from various applications. Here, we report the fabrication of flame-retardant, cellulose-based, thermal insulating polyHIPEs and their application for early fire warning. The polyHIPEs were synthesized from cellulose crystal-stabilized Pickering emulsions, containing ammonium salt of 1-hydroxyethylidene-1,1-diphosphonic acid as a reactive flame retardant, with or without MXene. The resulting polyHIPEs exhibited pre-designable external shapes, flexibility, robust compression, excellent thermal insulation with a thermal conductivity as low as 31.9 mW/(m·K), and high flame-retardant performance with a limit oxygen index up to 52.4% and with heat release rate and total heat release to be as low as 0.9 kJ/g and 13.7 W/g, respectively. The high thermal insulation and flame-retardant performance, combined with the responsive resistance of MXene, enabled the MXene-containing polyHIPEs to be excellent candidates for early fire warning, with warning to be realized within 3 s, with or without external power supply. Graphical abstract
危险品化学品经营许可证（带存储）