Hierarchical hydrogen bonds directed multi-functional carbon nanotube-based supramolecular hydrogels

Supramolecular hydrogels (SMHs) are three-dimensional networks filled with a large amount of water. The crosslinking force in the 3D network is always constructed by relatively weak and dynamic non-covalent interactions, and thus SMHs usually possess extremely high susceptibility to external environment and can show extraordinary stimuli-responsive, self-healing or other attractive properties. However, the overall crosslinking force in hydrogel networks is difficult to flexibly modulate, and this leads to limited functions of the SMHs. In this regard, hierarchical hydrogen bonds, that is, the mixture of relatively strong and relatively weak hydrogen bonds, are used herein as crosslinking force for the hydrogel preparation. The ratio of strong and weak hydrogen bonds can be finely tuned to tailor the properties of resultant gels. Thus, by delicate manipulation of the overall crosslinking force in the system, a hydrogel with multiple (thermal, pH and NIR light) responsiveness, autonomous self-healing property and interesting temperature dependent, reversible adhesion behavior is obtained. This kind of hierarchical hydrogen bond manipulation is proved to be a general method for multiple-functionality hydrogel preparation, and the resultant material shows potential for a range of applications. Carbon nanotube-based multiple responsive (thermal, pH, NIR light) supramolecular hydrogels with extraordinary self-healing performance and interesting adhesion behavior are prepared via simple mixing aqueous solution of carboxylic carbon nanotubes and polyethylene polyamine, and the ratio of strong hydrogen bonds to weak ones in hydrogel could be finely tuned by controlling the relative content of two precursors.