Tough,\nAnti-Swelling Supramolecular Hydrogels Mediated\nby Surfactant–Polymer Interactions for Underwater Sensors

Abstract

It\nis a great challenge for traditional hydrogel-based sensors\nto be effective underwater due to unsatisfactory water resistance\nand insufficient wet adhesion. Herein, a tough supramolecular hydrogel\naiming at underwater sensing is prepared by the modification of hydrophilic\npoly­(acrylic acid) (PAA) with a small amount of hydrophobic lauryl\nmethacrylate (LMA) in the presence of high concentrations of the cationic\nsurfactant cetyltrimethylammonium bromide (CTAB). Owing to the synergistic\neffects of the electrostatic interactions and hydrophobic associations\nof CTAB with the P­(AA-<i>co</i>-LMA) copolymer, the hydrogel\nwith a water content of approximately 58.5 wt % demonstrates outstanding\nanti-swelling feature, superior tensile strength (≈1.6 MPa),\nlarge stretchability (>900%), rapid room-temperature self-recovery\n(≈3 min at 100% strain), and robust wet adhesion to diverse\nsubstrates. Moreover, the strain sensor based on the hydrogel displays\nkeen sensitivity in a sensing range of 0–900% (gauge factor\nis 0.42, 3.44, 5.44, and 7.39 in the strain range of 0–100,\n100–300, 300–500, and 500–900%, respectively)\nand pronounced stability both in air and underwater. Additionally,\nthe hydrogel can be easily recycled by dissolving in anhydrous ethanol.\nThis work provides a facile strategy to fabricate eco-friendly, tough\nsupramolecular hydrogels for underwater sensing.