Super-elastic and mechanically durable MXene-based nanocomposite aerogels enabled by interfacial engineering with dual crosslinking strategy

Recently,MXenes have attracted considerable attention owing to their unique physical and chemical properties.Construction of MXenes to three-dimensional(3D)porous aerogel structures can play a critical role in realizing the profound implications of MXenes,especially for environmental remediation.Nevertheless,developing mechanically robust MXene-based aerogels with reversible compressibility under harsh conditions,such as liquid environments,remains challenging due to the insufficient interfacial strength between MXene nanosheets.Herein,3D porous MXene-based nanocomposite aerogels are developed by dual physical and chemical crosslinking strategy with poly(vinyl alcohol)and formaldehyde in this study.The developed MXenebased nanocomposite aerogels with designed interfacial engineering exhibit outstanding structural stability and extremely high reversible compressibility up to 98%strain as well as unprecedented mechanical durability(2000 cycles at 50%strain)in water environment.Moreover,the aerogels show adaptable compressibility when exposed to different solvents,which is explained with the Hansen solubility parameter.Thanks to their high compressibility in water,the robust MXene-based aerogels exhibit excellent methylene blue adsorption performance(adsorption capacity of 117.87 mg·g^(−1))and superior recycling efficiency(89.48%at the 3rd cycle).The porous MXene-based nanocomposite aerogels are also demonstrated with outstanding thermal insulation capability.Therefore,by synergistically taking their porous structure and super elasticity in liquid environment,the MXene-based aerogels show great promise in diverse applications including adsorption and separation,wastewater purification desalination,and thermal management.

Toughening Mechanism of Nanocomposite Physical Hydrogels Fabricated by a Single Gel Network with Dual Crosslinking-- The Roles of the Dual Crosslinking Points

A facile method to fabricate tough and highly stretchable polyacrylamide （PAM） nanocomposite physical hydrogel （NCP gel） was proposed. The hydrogels are dually crosslinked single network with the PAM grafted vinyl hybrid silica nanoparticles （VSNPs） as the analogous covalent crosslinking points and the reversible hydrogen bonds among the PAM chains as the physical crosslinking points. In order to further elucidate the toughening mechanism of the PAM NCP gel, especially to understand the role of the dual crosslinking points, the PAM hybrid hydrogels （H gels） and a series of poly（acrylamide-co-dimethylacrylamide） （P（AM-co-DMAA）） NCP gels were designed and fabricated. Their mechanical properties were compared with those of the PAM NCP gels. The PAM H gels are prepared by simply mixing the PAM chains with bare silica nanoparticles （SNPs）. Relative to the poor mechanical properties of the PAM H gel, the PAM NCP gel is remarkably tough and stretchable and also generates large number of micro-cracks to stop notch propagation, indicating the important role of PAM grafted VSNPs in toughening the NCP gel. In the P（AM-co-DMAA） NCP gels, the P（AM-co- DMAA） chains are grafted on VSNPs and the polydimethylacrylamide （PDMAA） only forms very weak hydrogen bonds between themselves. It is found that mechanical properties of the PAM NCP gel, such as the tensile strength and the elongation at break, are enhanced significantly, but those of the P（AM-co-DMAA） NCP gels decreased rapidly with decreasing AM content. This result reveals the role of the hydrogen bonds among the grafted polymer chains as the physical crosslinking points in toughening the NCP gel.