Ester Crosslinking Enhanced Hydrophilic Cellulose Nanofibrils Aerogel

The ester cross-linking of cellulose nanofibril (CNF) aerogel was carried out by a facile and highly effective gas–solid fluorinating reaction without the assistance of organic solvent. The fluorination achieved the coexistence of covalent cross-linking and more hydrophilic groups, simultaneously endowing the fluorine-treated CNFs (F-CNFs) aerogel with enduring water-durable and enhanced hydrophilic properties. Hydrogen bond interactions between cellulose nanofibers are replaced by covalent cross-linking of ester bonds, which makes the CNFs aggregate more tightly and thus facilitates the enhancement of mechanical properties of F-CNF aerogel. Meanwhile, the F-CNF aerogel exhibited ultralight weight, excellent mechanical properties (123.4 KPa at 85% strain), and water absorption (123.65 g/g), while having good shape memory performance. What’s more, there was not any exotic element introduced into F-CNFs, which can thus maximize the possibility for the final materials to maintain the excellent biological properties of the original CNFs.