Physically Cross-linked Hydrogels with Excellent Self-healing, Moldability, Antibacterial Activities and Adjustable Mechanical Properties

A simple strategy was developed to prepare a tough, self-healing, antibacterial and moldable hydrogel by introducing the natural polyphenolic compound tannic acid (TA) as a cross-linking center for hydrogen bonds. Polyvinyl alcohol (PVA)-TA hydrogel was prepared by physical mixing using PVA as a main component and TA as a cross-linker. There were two types of physical cross linking bonds in the PVA-TA hydrogel network, which were weaker hydrogen bonds between PVA molecular chains and stronger hydrogen bonds between PVA and TA molecules. The mechanical properties and self-healing ability could be adjusted by changing the contents of PVA and TA. The hydrogel possessed not only high mechanical strength (305 kPa tensile strength and 864 kPa compressive strength), moldability and excellent self-healing properties (95% self-healing efficiency) but also good antibacterial abilities against S. aureus and E. coli. In addition, after soaking the dried hydrogel in 90 celcius deionized water for 4 h, they could also regain their self-healing ability to a certain extent. The hydrogels have potential applications in the biomedical fields.