Composite hydrogels with host–guest interaction using cellulose nanocrystal as supramolecular filler

Abstract

The functional nanocomposite hydrogels are of great interest in the research field of materials science because of their improved mechanical performances and their ability to be used in a wider range of applications. Herein, the supramolecular composite hydrogels were developed and studied using a cellulose nanocrystal (CNC) as bio-based filler. The hydrogels were designed by introducing supramolecular bonding between host β-cyclodextrin (β-CD) and guest adamantane (Ad) groups at the interface between the highly dispersed CNC and the polymer matrix. For this purpose, the CNC surface was successfully modified with Ad to act not only as a reinforcing filler in the polymer network but also as a supramolecular cross-linker with the β-CD-modified polymer. Importantly, CNC exhibited the ability of preserving their good dispersibility in aqueous media, even after modification with the hydrophobic Ad group, owing to electrostatic repulsion among negative charges incorporated onto CNC surface. Furthermore, the modification of CNC with Ad contributed to the greater interfacial compatibility between the filler and the matrix. The present study therefore highlights that the toughness of a hydrogel can be improved by the incorporation of supramolecular bonding as reversible bonding at the filler/matrix interface, which sacrificially depletes the mechanical energy upon deformation of the gels.