Water‐Triggered Spontaneously Solidified Adhesive: From Instant and Strong Underwater Adhesion to In Situ Signal Transmission

Abstract

Developing conductive underwater glue for fast sealing and in situ monitoring is critical for ocean exploration yet remains a challenge. The fluidity of glue is a double‐edged sword that is favorable for molecule spreading and formation of interlocking bonding network yet also leads to leakage of conductive ions. Herein, a polymeric glue possessing good conductivity and exhibiting rapid, strong, and long‐lasting underwater adhesion on diverse substrates at various harsh environments and extreme temperatures is developed. For molecular design, the nitrogen heterocyclic motif that prevails in biomolecular recognition is encoded with water‐resistant benzene block in one pendant group to serve as underwater binding sites; ionic liquids (ILs) of [EMIM][BF4] is employed as the solvent for fast water exchange that triggers rapid adhesion. Simultaneously, the polymer‐IL interaction is regulated, with the assistance of the theoretical calculations, to retain sufficient ILs within the adhesive for sensing. Finally, the glue is applied for underwater sealing and in situ monitoring various physical signals, while the fluorescent property is utilized for underwater labeling. This study should provide a new design strategy for the next‐generation of multifunctional underwater adhesives and promote their applications.

Achieving strong, stable, and durable underwater adhesives based on a simple and generic amino-acid-resembling design

“…In these processes, the presence of water contributes to the electron transfer of the AMTD structure, which enables successful molecule crosslinking and thereby liquid-to-solid transition. [46][47][48] Distinct from most of the reported strategies which require multistep methods and harsh synthesis conditions, 10,12,32,38 this onestep process is time/energy effective and solvent-eliminating, making it promising for large-scale production.…”

“…7,8 To address these issues, diverse strategies have been proposed to develop polymeric and supramolecular underwater adhesives based on the principle of water repulsion via hydrophobic interactions or water absorption by leveraging hydrophilic or positive charge components. [9][10][11][12][13][14][15][16][17] However, with existing approaches, it is difficult to achieve strong, stable, and durable underwater adhesives for practical application. This is mainly because that the adhesives synthesized into solid states (e.g., films, [18][19][20] rubbers, [21][22][23] and gels, [24][25][26] ) have robust bulk strength Underwater adhesives have gained growing attention owing to their wide applications.…”

Molecular architecture regulation for the design of instant and robust underwater adhesives

“…It has been recognized that the hydrophobic components contribute to the exclusion of interfacial water molecules and establishment of underwater adhesion (17)(18)(19); the introduction of multiple hydrogen bonds into the matrix of adhesives can improve the mechanical properties; therefore, the precise design of the chemical structures to integrate hydrophobic group with hydrogen bond motif may be a useful way to design underwater adhesives. Distinguished from the adhesive proteins secreted by marine organisms mainly composed of adjacent hydrophobic and cationic amino acids, the phenyl and carboxyl group in phenylalanine can act as a hydrophobic component to repel water molecules for efficient interfacial interaction and serve as a hydrogen bond motif for matrix strengthening, respectively.…”

Scalable Underwater Adhesives with High-Strength, Long-Term, and Harsh-Environment Adhesion Enabled by Heterocyclic Chemistry

“…Heterocycles, an extraordinarily important class of compounds, have a wide range of applications in such as biomedicine, catalysis, and electronic/optical devices due to their unique structural features . However, the application potential of heterocycles in adhesive materials, especially for the unfavored water conditions, has not yet clearly recognized and understood . Among numerous kinds of heterocycles, thiadiazole compounds (TDZs) containing nitrogen and sulfur hetero atoms have attracted significant attention owing to their high structural activity, chemical and thermal stability.…”