Ultra-low temperature environments in the aerospace industry pose significant challenges to the performance of elastic materials in spacecraft and related equipment. at present,Most traditional inherently elastic materials usually lose their inherent elasticity in ultra-low temperature environments.. Existing solutions are mainly elastic aerogels based on carbon and ceramic structures; these emerging carbon and ceramic aerogels have promoted the development of elastic materials in ultra-low temperature environments,Its complex manufacturing process and high cost limit its further application.

In this context, the latest reports show a method made of low-cost chitosan and melamine-Formaldehyde resin composed of polymer aerogels, in liquid nitrogen temperature (77K) is super-elastic. Among polymer materials, polyimide(PI)It has a significant tolerance to extreme conditions.However, the thermal imidization after freeze-drying in the above strategy will inevitably lead to up40%The shrinkage deformation greatly impairs the elasticity.PICompressibility of Aerogels. in addition,Due to the polyamic acid (PAA) of incomplete salinity,PAASDecomposition in water can not be completely avoided, resulting in elasticPILow molecular weight of aerogel affects its resilience. Recent emergence of electrospun nanofibersPIaerogels provide an effective way to avoidPAASa lot of shrinkage and decomposition in the water,The combination of electrospinning processes complicates the overall manufacturing process and increases costs.

In view of this,The team of Professor Mingxin Ye and Professor Jianfeng Shen of Fudan University has developed a strategy based on mass-producible and low-cost oriented dimethyl sulfoxide crystals to assist freeze-gelation and freeze-drying, achieving covalently cross-linked polyimide.(PI)Aerogel at ultra-low temperature(4 K)Under the hyperelasticity (99%elastic compression strain), in severe thermal shock(ΔT=569 K)After the elastic loss is almost zero, and has a can withstand more.5000The fatigue resistance of the sub-compression cycle.

Figure 1. Schematic of construction of hyperelastic PI aerogel. PI aerogels with covalently cross-linked, radially distributed microstructures and different shapes were designed and synthesized.

Figure 2. Preparation of DMSO solvent covalently cross-linked PI aerogel.

high elasticityPImechanism of aerogel]

The author usesDMSOGood solubility, chemical imidization process and covalent cross-linking structure to manufacture.PIThe aerogel synergistically reduces the volume shrinkage of the resulting aerogel. ByDMSOprepared by chemical imidizationPIAerogel DisplayVolume shrinkage is less7.3%, far superior to thermally imidized19.5-25.3%. Covalent cross-linked structures are usually able to impartPIThe better heat resistance and mechanical properties of aerogels can inhibit the structural damage caused by thermal stress shock in high temperature thermal annealing.

Figure 3. Structure and morphology of PI aerogels.

Mechanical properties of highly elastic PI aerogels]

ThePIaerogelIn4 KIt also shows amazing super-elasticity at deep and low temperatures.,Even in suffering4 Kand573 Kbetween the thermal shock after,PIThe aerogel remains up99%strain compressibility and perfect recoverability, no significant structural damage was observed.

Figure 4. Mechanical properties of PI aerogels.

Figure 5. Mechanical properties of PI aerogels in various environments.