A hyperbranched polymer-based water-resistant adhesive:Durable underwater adhesion and primer for anchoring anti-fouling hydrogel coating

Direct deployment of gluing and achieving durable robust adhesion in water is challenging due to difficulty in repelling interface water.This work reports a novel hyperbranched polymer-based water-resistant adhesive(HBPBA)based on Michael addition reaction of multi-vinyl monomers with dopamine and 3-aminophenylboronic acid.Upon encountering water,the HBPBA forms coacervates whose hydrophobic chains aggregate to displace interface water,and meanwhile the catechols exposing outwards contribute to underwater adhesion.The HBPBA can strongly glue diverse substrates including PTFE,PE,PET,ceramic,Ti and stainless steel.The HBPBA can maintain stable adhesion in different environments,such as tap water,simulated sea water,PBS,and a wide range of pH solutions(pH 2 to 10)for 3 months,supposedly due to the complexation of catechol with boronic acid.Intriguingly,HBPBA film can be bonded to the titanium surface as a primer,which firmly anchors the antifouling PNAGAPCBAA hydrogel coating through copolymerization of remaining double bonds in HBPBA and NAGA plus CBAA.The PNAGA-PCBAA hydrogel-modified titanium is biocompatible and shows outstanding antifouling ability both in vitro and in vivo.This work proposes a new strategy for creating underwater deployable and water-resistant adhesives that may find promising applications in engineering and biomedical fields.

Light-controlled switchable underwater adhesive

Despite extensive efforts in designing and preparing switchable underwater adhesives,it is not easy to regulate the underwater adhesion strength locally and remotely.Here,we design and synthesize photoreversible copolymer of poly[dopamine methacrylamide-co-methoxyethyl-acrylate-co-7-(2-methacryloyloxyethoxy)-4-methylcoumarin].Due to the dynamic formation and breaking of chemical crosslinking networks within the smart adhesives,the material shows widely tunable adhesion strength from∼150 to∼450 kPa and long-range reversible maneuverability under orthogonal 254 and 365 nm ultraviolet light stimulation via the coumarin dimerization and cycloreversion.Moreover,the adhesive exhibits good circulation performance and stability in an acid–base environment.It also demonstrated that the bolt can be coated with the smart adhesive material for on-demand bonding.This design principle opens the door to the development of remotely controllable high-performance smart underwater adhesives.

Recent Progress of Mussel-Inspired Underwater Adhesives

Underwater adhesion is greatly desired in tissue transplantation, medical treatment, ocean transportation, and so on. However, common commercial polymeric adhesives are rather weakened and easily destroyed in water envi- ronment. In nature, some marine organisms, such as mussels, barnacles, or tube worms, exhibiting excellent under- water adhesion up to robust bonding on the rock of sea floor, can give exciting solutions to address the problem. Among these marine organisms, mussels exhibit unique underwater adhesion via the foot proteins of byssus. It has been verified that the catechol groups from the side chain of the mussel foot proteins is the main contribution to the unique underwater adhesion. Hence, inspired by the mussels＇ underwater adhesion, many mussel-mimetic polymers with catechol as end chains or side chains have been developed in the past decades. Here, we review recent progress of mussel-inspired underwater adhesives polymers from their catechol-functional design to their potential applica- tions in intermediates, anti-biofouling, self-healing of hydrogels, biological adhesives, and drug delivery. The re- view may provide basis and help for the development of the commercial underwater adhesives.

Low-molecular-weight supramolecular adhesive with resistance to low temperatures

The design of adhesive materials with strong adhesion capacity at low temperatures is a great challenge.Herein,we report a low-molecular-weight supramolecular adhesive that exhibits good adhesion performance to various surfaces at low temperatures(from-18℃ to-80℃).Moreover,this supramolecular adhesive has good adhesion ability in the presence of water.

Facile tuning of hydrogel properties by manipulating cationic-aromatic monomer sequences

Copolymer hydrogels formed from cationic and aromatic monomers with identical monomer compositions but different average sequences were synthesized by free-radical copolymerization in various solvents.We found that hydrogels with one-componentrich segments are mechanically stronger than those with adjacent-rich monomer sequences in water,while hydrogels with a rich cation-πadjacent sequence showed excellent mechanical strength and underwater adhesion in saltwater(0.7 M Na Cl).The molecular mechanisms for these behaviors are discussed in terms of polymer structures.This work reveals the importance of monomeric sequences in determining hydrogel properties and provides a facile approach to develop hydrogels with different properties but the same monomer composition.

Microfluidics-assisted optimization of highly adhesive haemostatic hydrogel coating for arterial puncture

Although common in clinical practice,bleeding after tissue puncture may cause serious outcomes,especially in arterial puncture.Herein,gelatin-tannic acid composite hydrogels with varying compositions are prepared,and their adhesive properties are further optimized in microfluidic channel-based simulated vessels for haemostasis in arterial puncture.It is revealed that the composite hydrogels on the syringe needles used for arterial puncture should possess underwater adhesion higher than 4.9 kPa and mechanical strength higher than 86.0 kPa.The needles coated with the gelatin-tannic acid composite hydrogel completely prevent blood loss after both vein and arterial puncture in different animal models.This study holds great significance for the preparation of haemostatic needles for vessel puncture,and gelatin-tannic acid hydrogel coated needles may help to prevent complications associated with arterial puncture.