Reversibly Compressible Supramolecular Aerogels with Low Density and Sound Insulation Performance

Abstract

self-assembly as a new class of effective method has proven to be promising for the construction of complex superstructures based on noncovalent interaction with tailor-made properties in a scalable and sustainable manner. [12,13] The principal advantage of noncovalent interactions is reversibility, which allows supramolecular hydrogels to be distinguished from the covalently cross-linked polymeric cousins by dynamic character. [14][15][16][17][18] In most cases, of particular interest is that supramolecular hydrogels can be divided into single-component hydrogels and multicomponent hydrogels and the latter greatly enriches the formation of new types of structures at various levels. [19] As supramolecular assemblies often cooperatively integrate two or more of the components, these assemblies can be endowed with unique synergistic properties rather than the mere combination of the individual properties of each component. [20,21] Aerogels are well-known flexible materials formed by replacing the liquid of a gel with the gas while retaining the 3D network structure. [22][23][24] Such materials have been widely utilized in a myriad of fields as a result of their striking properties, such as extremely low density, high porosity, and unique mechanical properties. [25][26][27][28][29][30] Up to now, various aerogels, such as carbon-based, silicon-based, and polymer aerogels, have been prepared through hydrothermal methods, chemical vapor deposition, 3D printing, and self-assembly. [31][32][33] Ideally, supramolecular aerogels can be derived from the parental hydrogels by depleting the contained water. Although there already appeared several supramolecular aerogels achieved from supramolecular organogels, hardly any were obtained from supramolecular hydrogels to the best of our knowledge. [23,24,[34][35][36] Compared with the mentioned above aerogels, supramolecular aerogels are achieved from small organic molecules in solvents with no requirement for any additional polymer binders and subsequently remove solvents, thus a supramolecular material with a 3D network structure is obtained. [7,37] Moreover, most of the supramolecular hydrogels consist of flexible fibers with a high aspect ratio. The fiber structure remaining after transferring to supramolecular aerogels gives them some mechanical properties to resist external stress stimulation, such as rigid or reversible compressibility. [38][39][40][41][42] Therefore, supramolecular aerogels are featured by simple preparation, low cost, easy degradation, energysaving, excellent mechanical properties, and environmental friendliness, which possess promising research prospects. [43] It is still a great challenge for supramolecular materials to be used as polymer systems. Here, reversibly compressible supramolecular aerogels with low density and sound insulation performance are reported, which are exclusively composed of small molecules. It is found that the mixture of melamine and isonicotinic acid can form supramolecular hydrogel. Then it could be transformed into aerogel v...

Heat‐Set Supramolecular Hydrogelation by Regulating the Hydrophilic–Lipophilic Balance for a Tunable Circularly Polarized Luminescent Switch

“…Conventionally, supramolecular hydrogels exhibit normal phase transition behaviors [6][7][8][9][10][11][12] of melting upon heating and solidifying upon cooling. While heat-set supramolecular gels exhibit totally opposite thermally induced phase behaviors, which are regarded as DOI: 10.1002/smll.202307948 isolated cases, [13][14][15][16][17][18][19][20][21][22][23] and have potential applications in fire extinguishers and postsurgery adhesion prevention. [24][25][26][27] However, theoretically speaking, higher temperature isn't in favor of physical gelation because of general molecular assembly into aggregates upon cooling.…”