Formulation and Optimization of a Tunable Natural Underwater Adhesive Hydrogel Based on Gelatin and Tannic Acid Enhanced by a Fatty Acid Publisher



Rezvani F ; Salehi Z ; Akrami M ; Tavafoghi M ; Ahmadi Tafti SM
Source: Journal of Industrial and Engineering Chemistry Published:2025

Abstract

In this study, a cost-effective, natural-based hydrogel adhesive with multifunctional properties was developed by gelatin (G) and tannic acid (TA), modified with stearic acid (SA) for wet environments. This modification introduced hydrophobic interactions and hydrogen bonding, enhancing the hydrogel's adhesive properties by removing water molecules from various surfaces. The coacervate hydrogel was characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The resulting Gelatin/Tannic Acid/Ethanol/Stearic Acid (GTE/SA) hydrogel exhibited underwater adhesion, forming a cross-linked coacervate matrix with high toughness (300–650 kJ/m3), adhesion strength (52–111 kPa on glass, 1770 kPa on wood), adhesion energy (>700 J) and tensile strength (>400 kPa), while maintaining high stretchability (up to 700 % strain). Using central composite design response surface methodology (CCD-RSM), the effects of tannic acid to gelatin ratio (TA/G) and working volume (ml) on mechanical properties and adhesion were analyzed, revealing optimal performance at a TA/G ratio of 0.94 (g/g) and volume of 10 (ml). The innovative use of the biomimetic properties of a natural stearic acid solution provides exceptional underwater adhesion capabilities through the mechanism of creating a waterproof surface. Additionally, the hydrogel exhibits antibacterial properties, tolerates a wide range of pH (3–9), and withstands ionic strengths (0–1 M NaCl). © 2025 Elsevier B.V., All rights reserved.