. 2021 Nov 24;13(23):4086. doi: 10.3390/polym13234086
© 2021 by the authors.
Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Figure 9.
Chemical structure of tannic acid, a tannin.