A scalable, efficient, and facile ambient drying approach for preparing low shrinkage, compressive, and superporous nano-cellulose-based aerogels via a physicochemical crosslinking strategy

Abstract

Ambient pressure drying (APD) is a scalable and efficient approach to preparing aerogels compared with traditional drying techniques. However, the scalable, efficient, and facile preparation of aerogels with a low shrinkage rate (SR) remains a great challenge, especially for starting materials insoluble or non-dispersible in alcohols. This study reports a physicochemical crosslinking strategy to prepare a nanocellulose-based aerogel with a low SR (∼10% in volume), high porosity (∼95%), low bulk density (∼50 mg cm⁻³), and compressive mechanical properties (stress of ∼26 kPa and recovery rate of ∼95% at 50% strain) via APD within 8 hours, saving ∼80% of the time compared to freeze drying for a similar sample size (>48 h for 10 cm³). The physicochemically crosslinked nanocellulose network was constructed by performing cyclic freeze–thaw treatment for the covalently crosslinked bacterial nanocellulose (BC) network (BGP) fabricated via the ring-opening reaction between epoxy functionalized BC and branched-polyethyleneimine (b-PEI). Furthermore, the developed BGP network can serve as a universal skeleton for functional nanomaterials, such as bentonite, CNTs, and MXene, to fabricate scalable advanced functional aerogels via the APD approach, expanding the application prospects from removal of water pollutants to fireproofing, sensing, EMI shielding, photothermal conversion, etc.