Rational design of adhesives for effective underwater bonding

Abstract

Underwater adhesives hold great promises in our daily life, biomedical fields and industrial engineering. Appropriate underwater bonding can reduce the huge cost from removing the target substance from water, and greatly lift working efficiency. However, different from bonding in air, underwater bonding is quite challenging. The existence of interfacial water prevents the intimate contact between the adhesives and the submerged surfaces, and water environment makes it difficult to achieve high cohesiveness. Even so, in recent years, various underwater adhesives with macroscopic adhesion abilities were emerged. These smart adhesives can ingeniously remove the interfacial water, and enhance cohesion by utilizing their special physicochemical properties or functional groups. In this mini review, we first give a detail introduction of the difficulties in underwater bonding. Further, we overview the recent strategies that are used to construct underwater adhesives, with the emphasis on how to overcome the difficulties of interfacial water and achieve high cohesiveness underwater. In addition, future perspectives of underwater adhesives from the view of practical applications are also discussed. We believe the review will provide inspirations for the discovery of new strategies to overcome the obstacles in underwater bonding, and therefore may contribute to designing effective underwater adhesives.

Underwater Bonding with a Biobased Adhesive from Tannic Acid and Zein Protein

“…Great success has been achieved over the decades from classic glues including epoxies, acrylates, and urethanes. , Once water enters the picture, however, creating strong adhesion becomes significantly more challenging . At the surfaces, hydration prevents materials from making robust contacts . Within the bulk, water may interact with polymers through hydrogen bonding to inhibit, degrade, or prevent cross-linking that is needed for cohesion.…”

“…4 At the surfaces, hydration prevents materials from making robust contacts. 5 Within the bulk, water may interact with polymers through hydrogen bonding to inhibit, degrade, or prevent cross-linking that is needed for cohesion. This phenomenon is related to water ingress when some petroleum-based glues deteriorate underwater.…”

Improving interfacial adhesive bond durability of a structural epoxy with steel using a tannic acid‐based additive for underwater applications

“…and cohesion (using special crosslinking agents, coacervates, stimuli such as light or temperature to promote underwater curing and crosslink density) components. 21 Several strategies which primarily rely on breaking down the hydration layer on the adherend surface have been reported to improve wet adhesion. However, these approaches have not yet been extended to structural adhesives as they demand a complex fabrication process.…”

“…Adhesive modification aimed to improve underwater bonding focuses on enhancing adhesion (introducing hydrophobic segments into the adhesive, utilizing hygroscopicity and swelling property, solvent exchange, special functional groups, etc.) and cohesion (using special crosslinking agents, coacervates, stimuli such as light or temperature to promote underwater curing and crosslink density) components 21 . Several strategies which primarily rely on breaking down the hydration layer on the adherend surface have been reported to improve wet adhesion.…”

Viscous, Hofmeister Effect‐Enhanced Macromolecular Adhesives for Effective Bonding in Seawater

“…Although achieving bonding in natural seawater is extremely challenging, and has not been reported so far, strategies to achieve underwater bonding in ideal static water have been proposed [13–16] . These strategies rationally utilize the hydrophobic segments and hydrophilic groups in the adhesive to displace or absorb the hydration film, establishing stable adhesion to the surface of underwater substrates [17] . For example, Liu and coworkers [18] designed a hydrophobic chains self‐aggregate hyperbranched polymer (HBP) adhesive, which exhibited rapidly strong adhesion to diverse materials.…”