Super-elasticity at 4\u2009K of covalently crosslinked polyimide aerogels with negative Poisson\u2019s ratio

Yang Cheng,Pei Dong,Wei Yao,Mingxin Ye,Jianfeng Shen,Pulickel M Ajayan,Yixiu Qin,John Matz,Xiang Zhang

doi:10.1038/s41467-021-24388-y

Yang Cheng, Pei Dong + Show 7 more

Open Access

https://doi.org/10.1038/s41467-021-24388-y

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Abstract

The deep cryogenic temperatures encountered in aerospace present significant challenges for the performance of elastic materials in spacecraft and related apparatus. Reported elastic carbon or ceramic aerogels overcome the low-temperature brittleness in conventional elastic polymers. However, complicated fabrication process and high costs greatly limited their applications. In this work, super-elasticity at a deep cryogenic temperature of covalently crosslinked polyimide (PI) aerogels is achieved based on scalable and low-cost directional dimethyl sulfoxide crystals assisted freeze gelation and freeze-drying strategy. The covalently crosslinked chemical structure, cellular architecture, negative Poisson’s ratio (−0.2), low volume shrinkage (3.1%), and ultralow density (6.1 mg/cm3) endow the PI aerogels with an elastic compressive strain up to 99% even in liquid helium (4 K), almost zero loss of resilience after dramatic thermal shocks (∆T = 569 K), and fatigue resistance over 5000 times compressive cycles. This work provides a new pathway for constructing polymer-based materials with super-elasticity at deep cryogenic temperature, demonstrating much promise for extensive applications in ongoing and near-future aerospace exploration.

Highlights

The deep cryogenic temperatures encountered in aerospace present significant challenges for the performance of elastic materials in spacecraft and related apparatus
We proposed a directional dimethyl sulfoxide crystal assisted freeze gelation and freeze-drying (DMSO-FGFD) strategy to construct covalently crosslinked PI aerogels with super-elasticity at deep cryogenic temperatures even down to 4 K
PI oligomers end-capped with anhydride were obtained through chemical imidization at room temperature by adding acetic anhydride and triethylamine into PAA precursors which were synthesized from 4,4’-oxydianiline (ODA) and 4,4’-oxydiphthalic anhydrides (ODPA) in Dimethyl sulfoxide (DMSO) solvent

Summary

Introduction

The deep cryogenic temperatures encountered in aerospace present significant challenges for the performance of elastic materials in spacecraft and related apparatus. Ceramic aerogels of BN nanoribbon and nanofibrous SiO2-based composites are in possession of compressive super-elasticity at 77 K14–17 These newly emerged carbon and ceramic aerogels make significant promotion for the development of elastic materials in deep cryogenic environments, while their complex fabrication process and high cost still raise misgivings. Freeze-casting techniques based on water-soluble PI precursors of poly (amic acid) ammonium salt (PAAS) are widely applied in the fabrication of elastic PI aerogels[23,24] Based on this strategy, various elastic PI aerogels composited with CNTs25,26, graphene[27,28], silica[29], MXene[30,31], and nanofibers[32,33] have been produced, endowing PI aerogels with such promising applications as electromagnetic shielding, oilwater separation, pressure sensors, etc.

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