Versatile Recyclable Kevlar Nanofibrous Aerogels Enabled by Destabilizing Dynamic Balance Strategy

Abstract

Aerogels are of great interest in diverse fields including thermal insulation, environmental protection, liquid separation, electromagnetic shielding, etc. However, the development of renewable and recyclable aerogels, especially synthetic polymer-based ones, remains an enormous challenge, which seriously hinders the practical application of aerogels. Herein, utilizing Kevlar nanofibers (KNFs) as representative synthetic polymer building blocks, a destabilizing dynamic balance (DDB) strategy is proposed to fabricate recyclable aerogels with high reprocessing consistency. More specifically, aprotic esters (e.g., di-tert-butyl decarbonate, DiBoc) and alkalis (e.g., potassium tert-butoxide, t-BuOK) are introduced to trigger the destabilizing dynamic balance between deprotonation–protonation of KNFs, resulting in a reversible sol–gel transition. Meanwhile, the duration of sol–gel transition (i.e., gelation) time, adjustable from 10^–2 to 10³ min, is compatible with versatile processing methods, such as static mould casting, dynamic wet spinning, dynamic blade coating and dynamic 3D printing. These unique advantages enable the fabrication of various KNF aerogel products (i.e., continuous fibers, continuous films, large-sized monoliths and 3D-printed articles) with low density (33–165 mg/cm³), high compressive modulus (up to 52 MPa), high specific surface area (360–404 m²/g) and low thermal conductivity (0.027–0.050 W/m·K). Notably, these properties are comparable or superior to that of previously reported KNF aerogels and far superior to that of recyclable aerogels. Compared with direct fabrication from raw materials, the DDB strategy reduces the cost by 50.5% and 82.5% when products are made from recycled aerogels and wet gels, respectively. Such cost reduction further increases with the number of recycling cycles, which is calculated as $275 per kilogram KNF aerogel with 5 cycles. This work develops extraordinary KNF aerogels those can be recycled and reused, as well as provides a strategy that can be applied to design more recyclable aerogels.

Funding

Royal Society(NA170184); National Natural Science Foundation of China(52003290); Natural Science Foundation of Jiangsu Province(BK20220296)