Hydrosilylation Adducts to Produce Wide-Temperature Flexible Polysiloxane Aerogel under Ambient Temperature and Pressure Drying.

Despite incorporation of organic groups into silica-based aerogels to enhance their mechanical flexibility, the wide temperature reliability of the modified silicone aerogel is inevitably degraded. Therefore, facile synthesis of soft silicone aerogels with wide-temperature stability remains challenging. Herein, novel silicone aerogels containing a high content of Si are reported by using polydimethylvinylsiloxane (PDMVS), a hydrosilylation adduct with water-repellent groups, as a "flexible chain segment" embedded within the aerogel network. The poly(2-dimethoxymethylsilyl)ethylmethylvinylsiloxane (PDEMSEMVS) aerogel is fabricated through a cost-effective ambient temperature/pressure drying process. The optimized aerogel exhibits exceptional performance, such as ultra-low density (50 mg cm-3), wide-temperature mechanical flexibility, and super-hydrophobicity, in comparison to the previous polysiloxane aerogels. A significant reduction in the density of these aerogels is achieved while maintaining a high crosslinking density by synthesizing gel networks with well-defined macromolecules through hydrolytic polycondensation crosslinking of PDEMSEMVS. Notably, the pore/nanoparticle size of aerogels can be fine-tuned by optimizing the gel solvent type. The as-prepared silicone aerogels demonstrate selective absorption, efficient oil-water separation, and excellent thermal insulation properties, showing promising applications in oil/water separation and thermal protection.

Large-Scale, Mechanically Robust, Solvent-Resistant, and Antioxidant MXene-Based Composites for Reliable Long-Term Infrared Stealth.

MXene-based thermal camouflage materials have gained increasing attention due to their low emissivity, however, the poor anti-oxidation restricts their potential applications under complex environments. Various modification methods and strategies, e.g., the addition of antioxidant molecules and fillers have been developed to overcome this, but the realization of long-term, reliable thermal camouflage using MXene network (coating) with excellent comprehensive performance remains a great challenge. Here, a MXene-based hybrid network comodified with hyaluronic acid (HA) and hyperbranched polysiloxane (HSi) molecules is designed and fabricated. Notably, the presence of appreciated HA molecules restricts the oxidation of MXene sheets without altering infrared stealth performance, superior to other water-soluble polymers; while the HSi molecules can act as efficient cross-linking agents to generate strong interactions between MXene sheets and HA molecules. The optimized MXene/HA/HSi composites exhibit excellent mechanical flexibility (folded into crane structure), good water/solvent resistance, and long-term stable thermal camouflage capability (with low infrared emissivity of ≈0.29). The long-term thermal camouflage reliability (≈8 months) under various outdoor weathers and the scalable coating capability of the MXene-coated textile enable them to disguise the IR signal of various targets in complex environments, indicating the great promise of achieved material for thermal camouflage, IR stealth, and counter surveillance.