Self-Propelling Hydrogel/Emulsion-Hydrogel Soft Motors for Water Purification

We fabricate a kind of catalytic self-propelling hydrogel soft motor (H-motor) via a facile injection loading method with low energy consumption. The factors influencing the practicability of H-motors, including locomotive ability and reusability, are investigated. The succession of rapid bubble evolution and propulsion endows the millimeter-sized columnar H-motors with length/diameter of 1 a remarkable speed of 3.84 mm s^–1 in 10% (w/w) hydrogen peroxide (H₂O₂) solution. Moreover, the H-motors maintain undiminished propulsion capability and functionality even after repeated loading for 6 times. Additionally, we also fabricate emulsion-hydrogel soft motors (E-H-motors) templated from the oil/water (O/W) emulsion for the first time, which exhibit a faster speed of 4.33 mm s^–1 under the same conditions. It can be ascribed to the additional liberation of low-boiling oil phase stored in the emulsion-hydrogels caused by catalytic reaction heat, which is appropriate for larger propulsive situations. The stabilized, efficient, and reusable H-motors are selected for industrial effluents purification to fit the imperious demands about the disposal of organic pollutants in water. The synergy effect between catalytic degradation and enhanced intermixing of the fluid flow around the miniaturized soft motors gives rise to an effective and exhaustive removal of organic contaminants

Self-Propelling Hydrogel/Emulsion-Hydrogel Soft Motors for Water Purification

We fabricate a kind of catalytic self-propelling hydrogel soft motor (H-motor) via a facile injection loading method with low energy consumption. The factors influencing the practicability of H-motors, including locomotive ability and reusability, are investigated. The succession of rapid bubble evolution and propulsion endows the millimeter-sized columnar H-motors with length/diameter of 1 a remarkable speed of 3.84 mm s^–1 in 10% (w/w) hydrogen peroxide (H₂O₂) solution. Moreover, the H-motors maintain undiminished propulsion capability and functionality even after repeated loading for 6 times. Additionally, we also fabricate emulsion-hydrogel soft motors (E-H-motors) templated from the oil/water (O/W) emulsion for the first time, which exhibit a faster speed of 4.33 mm s^–1 under the same conditions. It can be ascribed to the additional liberation of low-boiling oil phase stored in the emulsion-hydrogels caused by catalytic reaction heat, which is appropriate for larger propulsive situations. The stabilized, efficient, and reusable H-motors are selected for industrial effluents purification to fit the imperious demands about the disposal of organic pollutants in water. The synergy effect between catalytic degradation and enhanced intermixing of the fluid flow around the miniaturized soft motors gives rise to an effective and exhaustive removal of organic contaminants

Oil Absorbents Based on Melamine/Lignin by a Dip Adsorbing Method

Effective removal of oils and leakage chemicals from water is of significance in oceanography, environmental protection, and industrial production. Materials that can reduce environmental pollution are in high demand. Herein, we have developed a facile synthesis of ultralight, high-hydrophobic, and superoleophilic sponges (UHS sponges) through a dip adsorbing process based on lignin and commercially available melamine sponges. The obtained UHS sponges consist of an interconnected structure with high porosity and ultralow density (6.4 mg cm^–3). As the hydrophobic carbon coating of the skeleton and its microstructure trapping the air, the UHS sponge exhibits high-hydrophobicity and superoleophilicity, which are beneficial to its applications in oil–water separation. Besides lignin, other biomass like tannin is also suitable as the modification agent to prepare UHS sponges via a dip adsorbing method. As a result, this novel sponge exhibits excellent oil/water separation performance such as high selectivity, good recyclability, and oil absorption capacities up to 217 times of its own weight or 99 vol % of its own volume. We believe that this dip adsorbing method resultant sponge is highly promising as an ideal oil absorbent in oil spill recovery and environmental protection

Fabrication of Anion-Exchange Polymer Layered Graphene–Melamine Electrodes for Membrane Capacitive Deionization

A novel nitrogen-doped reduced graphene sponge composite (NRGS) is fabricated by using melamine sponge to restrain the aggregation of graphene sheets during reduction. The anion-exchange polymer layered graphene composites (A-NRGS) are prepared by coating the surface of the NRGS electrode with cross-linked poly­(vinyl alcohol) with quaternization modification (C-qPVA). With the help of a melamine sponge to suppress the agglomerate of graphene sheets, the NRGS exhibits a unique three-dimensional (3D) interconnected porous structure with abundant nitrogen doping of 5.2%. Its specific surface area is up to 241 m²/g. In addition, the enhanced wettability of A-NRGS composites favors the diffusion of ion from the electrolyte to electrode. Therefore, A-NRGS composites have excellent electrochemical capacity (184 F/g). The membrane capacitive deionization (MCDI) performance for A-NRGS electrode (11.3 mg/g) is higher than that of pristine reduced graphene oxide (RGO) (6.2 mg/g) and NRGS (8.6 mg/g) electrodes. All the results demonstrate that A-NRGS composites can be a promising candidate for CDI and other electrochemical applications

Oil Absorbents Based on Melamine/Lignin by a Dip Adsorbing Method

Effective removal of oils and leakage chemicals from water is of significance in oceanography, environmental protection, and industrial production. Materials that can reduce environmental pollution are in high demand. Herein, we have developed a facile synthesis of ultralight, high-hydrophobic, and superoleophilic sponges (UHS sponges) through a dip adsorbing process based on lignin and commercially available melamine sponges. The obtained UHS sponges consist of an interconnected structure with high porosity and ultralow density (6.4 mg cm^–3). As the hydrophobic carbon coating of the skeleton and its microstructure trapping the air, the UHS sponge exhibits high-hydrophobicity and superoleophilicity, which are beneficial to its applications in oil–water separation. Besides lignin, other biomass like tannin is also suitable as the modification agent to prepare UHS sponges via a dip adsorbing method. As a result, this novel sponge exhibits excellent oil/water separation performance such as high selectivity, good recyclability, and oil absorption capacities up to 217 times of its own weight or 99 vol % of its own volume. We believe that this dip adsorbing method resultant sponge is highly promising as an ideal oil absorbent in oil spill recovery and environmental protection

Fabrication of Tunable Janus Microspheres with Dual Anisotropy of Porosity and Magnetism

This work presents a facile approach to produce a novel type of Janus microspheres with dual anisotropy of porosity and magnetism based on Pickering-type double emulsion templates. A stable aqueous Fe₃O₄ dispersion-in-oil-in-water (W_F/O/W) double Pickering emulsion is first generated by using hydrophobic silica and hydrophilic mesoporous silica particles as stabilizers. Janus microspheres with multihollow structure possessing magnetite nanoparticles concentrated on one side of the microspheres are obtained after polymerization of the middle oil phase of the double emulsion under a magnetic field. The resultant Janus microspheres are characterized by optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX). Moreover, we have systematically investigated the influences of Fe₃O₄ particle concentration, hydrophobic silica particle content, and volume ratio of the inner water phase to middle oil phase (W_F/O) on the double emulsion formation and consequently on the structure of the resulting Janus microspheres. Our results show that the distribution of the multihollow structures within the prepared microspheres can be accurately tailored by adjusting the ratio of W_F/O. In addition, the obtained Janus microsphere can be fairly orientated under a magnetic field, making them a potential candidate for synthesizing Janus membrane

Renewable Lignin-Based Xerogels with Self-Cleaning Properties and Superhydrophobicity

A novel dissocyanate-modified lignin xerogel is facilely prepared using renewable lignin as precursors via a sol–gel process and ambient pressure drying method. The xerogel possesses high performance in self-cleaning and superhydrophobicity with no need for further hydrophobic modification. Furthermore, the xerogel obtained can find potential applications in absorbents, coatings, and scaffolds

A Triblock Copolymer Design Leads to Robust Hybrid Hydrogels for High-Performance Flexible Supercapacitors

We report here an intriguing hybrid conductive hydrogel as electrode for high-performance flexible supercapacitor. The key is using a rationally designed water-soluble ABA triblock copolymer (termed as IAOAI) containing a central poly­(ethylene oxide) block (A) and terminal poly­(acrylamide) (PAAm) block with aniline moieties randomly incorporated (B), which was synthesized by reversible additional fragment transfer polymerization. The subsequent copolymerization of aniline monomers with the terminated aniline moieties on the IAOAI polymer generates a three-dimensional cross-linking hybrid network. The hybrid hydrogel electrode demonstrates robust mechanical flexibility, remarkable electrochemical capacitance (919 F/g), and cyclic stability (90% capacitance retention after 1000 cycles). Moreover, the flexible supercapacitor based on this hybrid hydrogel electrode presents a large specific capacitance (187 F/g), superior to most reported conductive hydrogel-based supercapacitors. With the demonstrated additional favorable cyclic stability and excellent capacitive and rate performance, this hybrid hydrogel-based supercapacitor holds great promise for flexible energy-storage device

Versatile Fabrication of Nanocomposite Microcapsules with Controlled Shell Thickness and Low Permeability

Novel ethyl phenylacetate (EPA)-loaded nanocomposite microcapsules with polyurea (PU) /poly (melamine formaldehyde) (PMF) shells were facilely and fabricated: by using silica nanoparticle-stabilized oil-in-water (o/w) emulsion template and subsequent interfacial reaction and in situ polymerization. SiO₂ nanoparticles absorbed at the interface between oil and water to stabilize the o/w emulsions. The oil droplets containing EPA, isophorone diisocyanate (IPDI) and tolylene 2,4-diisocyanate-terminated poly (propylene glycol) (PPG-TDI) were subsequently reacted with MF prepolymer (pre-MF) dissolved in water phases. The interfacial reaction between pre-MF and IPDI produced interior PU walls. Meanwhile, the in situ polymerization of pre-MF generated exterior PMF walls. It was found that these in/out double walls were compact together. The resulting capsules had spherical shapes and rough exterior surfaces, and could be easily isolated, dried, and redispersed in epoxy resins. The size of the produced microcapsules was dependent on the concentration of SiO₂ nanoparticles. The dynamic thermal gravimetric analysis (TGA) demonstrated that the capsules showed excellent thermal stability with little weight loss when exposed at 150 °C for 2 h. Interestingly, with a double PU/PMF shell, these capsules exhibited an extra-low permeability. Moreover, these microcapsules can also demonstrate exceelent magnetic responsiveness after introducing magnetic nanoparticles inside. We believe our microcapsules could be potential candidates in microcapsule engineering, self-healing composites, and drug-carrying systems

Thermoresponsive Melamine Sponges with Switchable Wettability by Interface-Initiated Atom Transfer Radical Polymerization for Oil/Water Separation

Here we have obtained a temperature responsive melamine sponge with a controllable wettability between superhydrophilicity and superhydrophobicity by grafting the octadecyltrichlorosilane and thermoresponsive poly­(<i>N</i>-isopropylacrylamide) (PNIPAAm) onto the surface of melamine sponge skeletons. The whole process included the silanization in which step the rough surface with low surface energy and the NH₂ were provided, and the atom transfer radical polymerization which ensured the successful grafting of PNIPAAm onto the skeleton’s surface. The product exhibits a good reversible switch between superhydrophilicity and superhydrophobicity by changing the temperature below or above the lower critical solution temperature (LCST, about 32 °C) of PNIPAAm, and the modified sponge still retains a good responsiveness after undergoing two temperature switches for 20 cycles. Simultaneously, the functionalized sponges could be used to absorb the oil under water at 37 °C, and they released the absorbed oil in various ways under water at 20 °C, showing wide potential applications including oil/water separation