Hydrogel with Robust Adhesion in Various Liquid Environments by Electrostatic-Induced Hydrophilic and Hydrophobic Polymer Chains Migration and Rearrangement.

Hydrogels with wet adhesion are promising interfacial adhesive materials; however, their adhesion in water, oil, or organic solvents remains a major challenge. To address this, a pressure-sensitive P(AAm-co-C18 )/PTA-Fe hydrogel is fabricated, which exhibits robust adhesion to various substrates in both aqueous solutions and oil environments. It is demonstrated that the key to wet adhesion under liquid conditions is the removal of the interfacial liquid, which can be achieved through rational molecular composition regulation. By complexing with hydrophilic polymer networks, phosphotungstic acid (PTA) is introduced into the hydrogel network as a physical cross-linker and anchor point to improve the cohesion strength and drive the migration of polymer chains. The migration and rearrangement of hydrophilic and hydrophobic polymer chains on the hydrogel surface are induced by the electrostatic interactions of Fe3+ , which create a surface with interfacial water- and oil-removing properties. By co-regulating the hydrophilic and hydrophobic polymer chains, the P(AAm-co-C18 )/PTA-Fe hydrogel is able to act as a pressure-sensitive adhesive under water and oils with adhesion strength of 92.6 and 90.0 kPa, respectively. It is anticipated that this regulation strategy for polymer chains will promote the development of wet adhesion hydrogels, which can have a wide range of applications.

Multifunctional superhydrophobic adsorbents by mixed-dimensional particles assembly for polymorphic and highly efficient oil-water separation.

Supra-wetting materials, especially superhydrophobic absorption materials, as an emerging advanced oil-water separation material have attracted extensive concern in the treatment of oil spillage and industrial oily wastewater. However, it is still a challenge to fabricate robust and multifunctional superhydrophobic materials for the multitasking oil-water separation and fast clean-up of the viscous crude oil by an environment-friendly and scalable method. Herein, a solid-solid phase ball-milling strategy without chemical reagent-free modification was proposed to construct heterogeneous superhydrophobic composites by using waste soot as the solid-phase superhydrophobic modifier. A series of covalent bond restricted soot-graphene (S-GN) or soot-Fe3O4 (S-Fe3O4) composite materials with a peculiar micro-nano structure are prepared. Through "glue+superhydrophobic particles" method, the prepared soot-based composite particles are facilely loaded on the porous skeleton of the sponge to obtain multifunctional superhydrophobic adsorbents. The reported superhydrophobic adsorbents exhibited robust chemical and mechanical stability, convenient magnetic collection, the high oil absorption capacity of 60-142 g g-1, durable recyclability (>250 cycles), efficient separation efficiency (>99.5%) and outstanding self-heated performance, which enable them to be competent for oil-water separation in multitasking and complex environment (floating oils, continuous oil collection, oil-in-water emulsion, and viscous oil-spills).

Three-dimensional adsorbent with pH induced superhydrophobic and superhydrophilic transformation for oil recycle and adsorbent regeneration.

With the development of research on superwettability materials, superhydrophobic and superoleophilic materials show superior separation ability in oil-water separation due to their excellent oil-water selectivity. However, due to the super wetting ability of the oil to the material, it is difficult to clean and reuse after adsorbing the oil spill. Therefore, how to realize the complete regeneration of superhydrophobic and superoleophilic materials is still a worldwide problem. In this paper, the controlled adsorption-desorption process of oil and the complete regeneration of materials are realized by pH induced superwettability transformation. We fabricate a pH-responsive oil-water separation sponge by a method of simply impregnating the carboxyl and alkyl group modified SiO2 nanoparticles on the surface of melamine sponge (MS) skeleton, which can change the wettability from superhydrophobicity and superhydrophilicity through protonation and deprotonation in different pH solutions. The experiment results indicate that the sponge is superhydrophobic and superoleophilic in acid and neutral solution, and can adsorb oil in water. While in basic solution, it becomes superhydrophilic and underwater superoleophobic, which can release the adsorbed oil. With the help of a vacuum pump, we can use this wettability transition to achieve a continuous oil adsorption and desorption process. These findings offer a new preparation method of regenerative 3D adsorption materials like MS in oil-water separation.

Study of Oil Dewetting Ability of Superhydrophilic and Underwater Superoleophobic Surfaces from Air to Water for High-Effective Self-Cleaning Surface Designing.

The superhydrophilic self-cleaning surface can perfectly deal with oil pollution, which cannot be realized by the superhydrophobic surface. This research is designed to study the mechanism of wetting behavior of superhydrophilic coating with different function groups and guide to design a stable self-cleaning surface. We prepare several hydrophilic coatings including nonionic, ionic, and zwitterionic coatings to investigate their self-cleaning performance underwater when they have been polluted by oil in the dry state. The chemical composition, surface roughness, static and dynamic wettability, underwater oil adhesive force, and swelling degree of the coatings are studied to explore their oil dewetting mechanism. The results indicate that the wettability of the coating to water and oil is the key factor to determine the self-cleaning performance. The smooth 3-sulfopropyl methacrylate potassium salt (SA) anionic coating shows the best self-cleaning performance even when polluted by heavy crude oil in the dry state in air. It is also found that in the dry state, the rough hydrophilic anionic surface will lock up the oil in the structures and then lose its self-cleaning ability underwater, whereas the oil droplet can detach from the smooth coating surface quickly. Meanwhile, the superhydrophilic and underwater superoleophobic SA anionic surfaces also exhibit excellent anti-fogging and oil-water separation performance.

Performance evaluation of mercapto functional hybrid silica sol-gel coating and its synergistic effect with f-GNs for corrosion protection of copper surface.

A nanocomposite coating comprising mercapto functional hybrid silica sol-gel coating and functionalized graphene nanoplates nanocomposite coatings with advanced anticorrosive properties was prepared by a sol-gel method. In this study, graphene oxide (GO) nanoplates were silanized using 3-aminopropyltriethoxysilane (APTES) to obtain functional graphene nanoplates (f-GNs). The f-GNs were characterized by FTIR, XRD, XPS, TEM, AFM and TGA techniques. The functionalized graphene nanoplates were chemically bonded to a sol-gel matrix and showed good dispersion in the sol. Then, silica hybrid sol-gel nanocomposites with raw GO and different amounts of f-GNs were applied on the copper surface. Uniform, defect-free and adherent sol-gel films were obtained. Various corresponding methods were used to investigate the nanocomposite coating's properties. The corrosion resistance of copper significantly improved after being coated with mercapto functional hybrid silica sol-gel. The addition of f-GNs to the mercapto functional silica sol-gel coatings further improved the corrosion resistance due to a synergistic effect. Moreover, with an increase in the amount of f-GNs in the nanocomposite coating, the nanocomposite showed improved corrosion resistance. The nanocomposite containing 0.1 wt% f-GNs can efficiently protect the copper substrate from corrosion. This improvement was primarily attributed to the homogeneous dispersion of the f-GNs in the silica gel matrix and their effective barrier against corrosive molecules and ions. However, adding raw GO or excess f-GNs to the silica hybrid sol-gel coating had a negative effect on the corrosion resistance.