Aerogel is a kind of lightweight and porous nano material, which has extremely broad application prospects in high-tech fields such as aerospace, national defense, and civil fields such as construction and industrial pipeline insulation. According to the component properties of the pore wall materials, aerogels can be divided into inorganic aerogels (such as the only commercially available silica aerogels) and organic polymer aerogels (such as phenolic resin aerogels). Etc.) and carbon aerogels. How to obtain new high-performance/multifunctional aerogel materials through structural design, chemical assembly, and chemical technology is still one of the important basic research topics facing this field.
Recently, the aerogel team led by Zhang Xuetong from the Suzhou Institute of Nanotechnology, Chinese Academy of Sciences cooperated with researchers from Beijing Institute of Technology, and made some important progress in the field of polymer aerogels:
First, the zero-dimensional, one-dimensional or two-dimensional nanomaterials are uniformly dispersed in a liquid medium. As long as the concentration is within an appropriate range, the nanoparticles can contact each other to form a dynamic network. The second component that interacts with the nanoparticle interface is selected and introduced into the primary network system. At this time, the second component will preferentially adsorb on the surface of the nanoparticles. Subsequently, in-situ polymerization/curing/crosslinking of the second component is initiated to achieve "conformal" coating of the primary network. In this way, the dynamic network formed by the nanoparticles is immediately fixed. Then the solvent is removed by freeze-drying or supercritical drying to obtain elastic and porous aerogel three-dimensional material. This new type of aerogel preparation technology can be called "primary network conformal growth" technology. Scientists from the Suzhou Institute of Nanotechnology, Chinese Academy of Sciences and Beijing Institute of Technology worked closely together to propose this new technology for preparing aerogels, and used them to prepare elastic polypyrrole aerogels and polypyrrole/silver coaxial nanowire aerogels. An ideal sensing material with "zero" temperature coefficient of resistance (TCR) was obtained (as shown in Figure 1). The "temperature self-compensation" pressure sensor constructed with this aerogel material has high stability (TCR≤0.86 × 10-3 /οC), high sensitivity (0.33 kPa-1), short response time (1 ms), and low detection Limit (4.93 Pa) and other advantages. In addition, these aerogel materials can also be processed into pressure-sensitive smart Joule heaters. These research results have been published on ACS Nano 2015, 9, 4244-4251 and Scientific Reports 4: 4792.
Secondly, by introducing a crystalline phase into the water-soluble polymer hydrogel as a physical cross-linking point and a mechanically enhanced skeleton, an aerogel based on host-guest inclusions—α-cyclodextrin and polymer Ethylene glycol supramolecular polypseudorotaxane aerogel. From the structural point of view, this kind of aerogel is composed of unique two-dimensional graphene-like sheets three-dimensionally assembled; at the same time, by adjusting the molar ratio and concentration of cyclodextrin and polyethylene glycol, the sheet can be realized Simple control of the size of the layer structure and the crystal structure. These studies have shown that with supramolecular hydrogel as the precursor, a new kind of aerogel can be prepared through supercritical fluid technology: supramolecular aerogel! Since this aerogel skeleton is an infusible pipeline crystal structure coated with a polyethylene glycol crystal layer, it has good thermal stability, and polyethylene glycol, which is not involved in pipeline crystallization, is an excellent phase change energy storage material. Therefore, the obtained supramolecular aerogel can be used as a new multifunctional solid-solid phase change energy storage material. That is to say, by organically fusing the aerogel material with excellent heat insulation performance and the phase change energy storage material, the material itself can absorb and store energy while maintaining heat insulation, and release the stored energy at the right time. Energy, which can maximize the use of energy (as shown in Figure 2). The results of this research have been published online in ACS Nano, a well-known journal of the American Chemical Society. (DOI: 10.1021/acsnano.5b05281).
These work have been strongly supported by the National Natural Science Foundation of China (51572285, 21373024, 21404117), the Natural Science Foundation of Jiangsu Province (BK20151234, BK20140391), the Postdoctoral Fund of Jiangsu Province (1401066C) and the Hundred Talents Program of the Chinese Academy of Sciences.
Figure 1. Stress sensing properties of polypyrrole/silver coaxial nanowire composite aerogel
Figure 2. The structure of supramolecular aerogel and the schematic diagram of phase change energy storage-thermal insulation.
