Supramolecular hydrogel of poly(vinyl alcohol)/chitosan: A dual cross-link design

Supramolecular hydrogels are increasingly fascinating soft polymeric materials formed by noncovalent interactions. Poly(vinyl alcohol) (PVA), chitosan and graphite oxide (GO), good biocompatibility, and nontoxicity, are green materials with potential applications in biomaterials. Herein, a dual cross-link supramolecular hydrogel of PVA/chitosan in the presence of GO was prepared. Without addition of any organic cross-linker, the dual-network PVA/chitosan hydrogel was obtained, namely GO nanosheets as 2D cross-linker and H-bonding between PVA chains. For one thing, GO nanosheets induce the physical network formation through electrostatic interaction between positively charged PVA, chitosan, and negatively charged GO. For another, PVA chains can be connected by H-bonding through freezing/thawing measurements, resulting in the formation of another physical network. To investigate the performance of the PVA/chitosan/GO hydrogel, infrared spectrum, swelling test, thermal analysis, rheological study, and self-healing tests were conducted. The result showed that PVA/chitosan hydrogel in the presence of GO is not only self-healable, but also pH-responsive and temperature-dependent.