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

Abstract

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.