New Underwater Adhesive Achieves 1.1 MPa Strength in 10 Seconds for Mechanical Systems

📌 Article Summary

An innovative aqueous adhesive has been developed based on a supramolecular adhesive assembly, achieving high underwater adhesion strength of up to 1.1 megapascal (MPa) within just 10 seconds. This adhesive uses a solvent-exchange mechanism coupled with Marangoni flow to remove the surface water layer and assemble a cohesive, water-resistant adhesive network, with the added advantage of recyclability. Its notable mechanical performance and rapid fixation make it ideal for sustainable industrial and marine applications.

🔧 Challenges of Underwater Adhesion

Hydration layers of water on submerged surfaces form a major obstacle to achieving strong and effective adhesion to materials. Water molecules line up on the surface to form a liquid layer that prevents the adhesive from contacting the material directly, which weakens adhesion strength.

Conventional adhesives face multiple limitations such as slow curing, the need for photoinitiators, the release of reactive gases, and sensitivity to aqueous environments. In addition, environmental concerns related to certain chemical compounds such as PFAS highlight the need to develop new adhesives that combine speed, strength, and recyclability.

🔥 Structural Composition and Chemical Properties of the BP16TPB Adhesive

The new adhesive is based on the BP16TPB compound, consisting of aromatic bis-urea cations linked by hydrogen bonds, flexible 16-carbon alkyl chains, and tetraphenylborate anions. Its properties were analyzed using advanced spectroscopic techniques such as NMR, FT-IR, XPS, and thermal analysis tools such as DSC and TGA.

The adhesive is prepared by dissolving BP16TPB in DMSO at a concentration of approximately 0.2 g per mL, where it assembles molecularly into supramolecular oligomers based on noncovalent and reversible interactions.

⚡ Working Mechanism and Underwater Surface Dynamics

The main interaction relies on the exchange of DMSO with water, which leads to the generation of a large surface-tension gradient, causing Marangoni flow that helps remove the surface water layer quickly.

DMSO gradually diffuses into the surrounding aqueous medium during the first 25 minutes, and this process is accompanied by the transformation of the adhesive from dispersed oligomers into dense, strong supramolecular coacervates.

Monitoring the changes using spectroscopic methods aimed at tracking molecular reorganization showed the initial concentration of alkyl chains at the surface, followed later by the movement of anions and cations to the surface, with the formation of a network linked by hydrogen interactions, π-π stacking, and hydrophobic interactions.

🔩 Mechanical Performance and Reliability Under Different Conditions

• The adhesive reaches 1.1 MPa lap-shear strength on porcelain within 10 seconds, increasing to 1.3 MPa within 5 minutes.
• It shows similarly strong performance on copper (1.1 MPa), epoxy (0.7 MPa), and polyamide materials (0.5 MPa).
• The effects of acidity, alkalinity, and salinity are eliminated without a noticeable loss of strength, confirming its environmental stability.
• The adhesive maintains more than 0.8 MPa after 250 days of water immersion.
• Static load tests showed the ability to support a 2 kg weight underwater for more than 3 years without failure.
• It offers recyclability through decomposition and reconstitution without loss of strength over 8 repeated cycles.

🏭🚗 Advanced Industrial and Marine Applications

The fast adhesion and high strength characteristics allow this adhesive to be used in the repair and maintenance of marine structures and submarines, and for sealing underwater pipeline leaks without the need for removal or drying.

The adhesive can be applied easily using a syringe directly onto multi-material surfaces such as glass, porcelain, copper, and plastic, providing a versatile solution for the energy and marine construction industries.

Its stability in acidic, alkaline, and saline environments expands its range of use to include the fixation of environmental monitoring devices and oceanographic equipment.

By avoiding the use of harmful PFAS compounds, the adhesive offers a more environmentally friendly solution and has potential for use in biological fields such as repairing marine structures, although its biosafety has not yet been fully studied.

🔍 Conclusions and Future Prospects

BP16TPB presents an advanced model that combines rapid self-dewatering using Marangoni flow and dynamic supramolecular assembly to build a durable underwater adhesive network.

This technique represents a shift in the field of mechanical systems and marine adhesives, providing a recyclable alternative away from permanent covalent reactions.

The results indicate the possibility of extending this strategy to other supramolecular and ionic systems designed for the demands of harsh aqueous environments, with opportunities to develop smart, environmentally responsive materials whose assembly and dissolution can be controlled by solvents.

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