Tannic Acid Physically Cross-Linked Responsive Hydrogel

Tannic acid (TA) is a polyphenol-rich compound found in many natural plants. There are large numbers of phenolic hydroxyls at the terminal of the TA molecule, being capable of forming hydrogen bonds with hydrogen-bonding donating polymers such as polyvinylpyrrolidone (PVP) and then engineering a hydrogel network. The reversible switch between phenolic hydroxyls and quinones tuned by pH affords the dynamic nature of the resultant hydrogen bonds. The gels exhibit excellent shear-thinning and self-recovery properties. Moreover, the polyphenols can form coordinates with Fe(III) that link different TAs to form a hydrogel network. Hence, adding Fe(III) solution to the TA-PVP sol can form additional interactions inside the TA-PVP gel. The easy preparation of the dual-responsive gels with nontoxic raw materials may allow for its application in the biomedical field.