Flexible and Tough Cellulose Nanocrystal/Polycaprolactone Hybrid Aerogel Based on the Strategy of Macromolecule Cross-Linking via Click Chemistry

Cellulose nanocrystal (CNC) aerogel suffers from inherent brittleness, owing to the rigidity of crystals and the limited mobility between individual crystals. Conventional small molecule based cross-linking improves the toughness of CNC aerogel, but can hardly improve its flexibility. In this work, a macromolecule-based click cross-linking strategy with polycaprolactone diol as the cross-linker is employed to fabricate the CNC-PCL hybrid aerogel with enhanced toughness and flexibility. The molar ratio of CNC/PCL and the concentration of hydrogel are studied as the two key factors greatly affecting the mechanical performance of CNC-PCL aerogel. The resulted CNC-PCL hybrid aerogels show the highest compressive strength of 595 ± 100 kPa when the molar ratio of CNC/PCL is 1:0.1 (CP-0.1) and the highest shape recovery rate of 96.3 ± 2.5% when the molar ratio of CNC/PCL is 1:0.25 (CP-0.25). The surface polarity of CNC-PCL aerogel behaves as amphipathic due to the introduction of hydrophobic PCL. The thermal stability of CNC-PCL aerogel is also improved due to the high thermal stability of PCL. Therefore, this work provides a guidance for the preparation of nanomaterial-based aerogel with good mechanical properties and functionality by introducing functional polymers via click chemistry.