Amine-Cured Glycidyl Esters as Dual Dynamic Epoxy Vitrimers

It is of greater significance to develop amine-cured epoxy vitrimers than conventional epoxy-carboxylic acid vitrimers because amines are the most widely curing agents than carboxylic acids. Considering that the reaction of amines with glycidyl esters can skillfully create dynamic hydroxyl esters, so we synthesized aliphatic and aromatic glycidyl esters and then cured them by amine-curing agents containing disulfide bonds. Here, besides the generated hydroxyl esters, the dynamic disulfide bonds are also integrated into the cross-linked network to form dual dynamic vitrimers. The synthesized glycidyl esters show very high-efficiency curing reactivity due to the lower activation energy. The properties of dual dynamic vitrimers can be easily tuned via the proportion of aromatic and aliphatic glycidyl esters to realize the transition from the rubber state to glass state. Moreover, the combinations of enhancement and toughening are achieved via the addition of aromatic glycidyl esters into dual dynamic vitrimers without sacrificing the curing activity and reprocessing property. Compared with single dynamic vitrimers, the dual dynamic vitrimers exhibit excellent reprocessing performances and unique rheological characteristics due to the exchange reactions of transesterification and disulfide exchange at high temperatures, which enables them to be reprocessed at 180 °C for only 5 min

Rapid Fabrication of Porous Photothermal Hydrogel Coating for Efficient Solar-Driven Water Purification

Cost management and scalable fabrication without sacrificing the purification performance are two critical issues that should be addressed before the practical commercial application of solar-driven evaporators. To address this challenge, we report a porous photothermal hydrogel coating prepared by mixing the raw materials of sawdust (SD), carbon nanotubes (CNTs), and poly­(vinyl alcohol) (PVA), which was applied to undergo a blading–drying–rehydration process to prepare the evaporator. In the coating, the crystallized PVA gives the coating a solid skeleton and the sawdust endows the coating with a loose structure to sufficiently enhance the water transportation capacity. As a result, the evaporator coated with the hydrogel coating displays a high water transport rate and efficient evaporation performance along with excellent mechanical properties and stability. Water migrates vertically upward 5 cm within 4 minutes. The compressive stress of the rehydrated hydrogel coating reaches as high as 14.28 MPa under 80% strain. The water evaporation rate of the hydrogel coating-based evaporator reaches 1.833 kg m–2 h–1 corresponding to an energy efficiency of 83.29% under 1 sun irradiation. What is more, the hydrogel coating retains its excellent evaporation performance and stability after immersion in acid or alkali solution, ultrasound treatment, and long-time immersion in water. Under outdoor conditions, the water evaporation rate of the hydrogel coating-based evaporator is about 5.69 times higher than that of pure water. This study proposes a rapid, cost-effective, and scalable strategy for preparing a high-performance photothermal hydrogel coating that will find sustainable and practical application in solar-driven water purification