Unraveling the gallol-driven assembly mechanism of thermoreversible supramolecular hydrogels inspired by ascidians

Polyphenols-based supramolecular hydrogels have recently attracted much attention as smart materials for applications in several technologies. Although great advances have been made in this field, there is a challenging need for creating new versatile materials that combine synthesis simplicity and suitable functional properties. In this work, inspired by the hydrogen bonding ability of pyrogallol-bearing proteins found in ascidians, we explored a small gallol analog, gallic acid (GA), as a dynamic crosslinker of poly(vinyl alcohol) (PVA). The fundamentals of the supramolecular assembly mechanism of PVA/GA hydrogels are studied for understanding the final properties of the obtained thermo-reversible hydrogels. The polymer deacetylation degree was a key factor to control the gelation kinetics, morphology, and properties of the supramolecular materials. Furthermore, the intercalation of GA molecules between PVA chains produced polymer crystals with a new spatial arrangement, modifying the elastic modulus of the supramolecular network and increasing its stability in water. With remarkable fast gelation ability, ascidian-inspired PVA-GA hydrogels may provide a promising platform for a wide range of biomedical applications including topical drug delivery of therapeutic proteins, wearable electronic devices, and 3D printing. Gallic acid, a small polyphenolic compound with strong hydrogen-bonding ability, is studied as a dynamic crosslinker of poly(vinyl alcohol) for preparing thermosensitive hydrogels. Furthermore, insights about the involved mechanism are shown.