Preparation And Application Of Underwater Adhesive

Underwater adhesion has been a hot topic in the engineering field.In order to establish a bond between two adherends,an ideal adhesive should easily flow on the surface of the adherent to achieve good contact and adequate wetting,and cure in a reasonable time.However,it is difficult to achieve meet these requirements in a wet environment,especially in water,because,as a boundary layer,water weakens the interfacial adhesion of the adhesive,and as a solvent,destroy the integrity of the adhesive.Although some underwater adhesives have been developed,including polymeric adhesives,protein adhesives and biomimetic adhesives,there is still a great challenge to obtain ideal underwater adhesives.Most polymeric adhesives are made by polyurethane.Although the underwater adhesion strength can reach sevsral MPa,the poor biocompatibility of polyurethane adhesives limits its development in the biomedical field.Most of the current protein and biomimetic adhesives encounter some limitation.In order to obtain adhesives with high underwater adhesion strength,good biocompatibility,and long-term underwater adhesion,we prepared and characterized three types of adhesives:(1)We designed and prepared a polysaccharide-based underwater adhesive hydrogel with excellent biocompatibility.First,the catechol group is grafted to the chitosan chain to make it have adhesion ability underwater.Then ortho hydroxyl group on the dextran chain is oxidized to form an aldehyde group by sodium periodate,and then the two are blended to form hydrogel.The results show that this hydrogel has good underwater adhesion ability.When the ratio of CS-CH to ODEX is 3: 1,the maximum underwater adhesion strength of the hydrogel is reached.At the same time,hydrogels have excellent biocompatibility,no cytotoxicity,and have good prospects for biomedical applications.(2)We propose a convenient and versatile method to prepare underwater adhesion hydrogel.First,dopamine(DA)was grafted to oxidized carboxymethylcellulose(OCMC)to obtain dopamine-grafted oxidized carboxymethylcellulose(OCMC-DA).Second,the acrylamide(AM)monomer was conjugated with OCMC-DA by Schiff base reaction,and then polymerized to form OCMC-DA/PAM hydrogel.The results show that the excellent underwater adhesion properties of this hydrogel are used to solve the problem that most hydrogels do not have underwater adhesion strength.The maximal adhesion of hydrogel was shown when the G’ and G’’ was very close.In addition,excellent mechanical properties and biocompatibility make this hydrogel very suitable for biomedical applications.Last but not least,this adhesion strength can last for two weeks in water.These results indicate that OCMC-DA/PAM hydrogels are a very suitable and promising underwater adhesion material.(3)We prepared a hydrophobic nano-composite underwater adhesive,which is made of a solid-liquid blending system that is simple and easy to operate.Based on the difference between the electronegativity of liquid polydimethoxysiloxane(PDMS)and particle polytetrafluoroethylene(PTFE),the electrostatic interaction is used to form the basic composite adhesive PDMS / PTFE,and then the etraethyl silicate(TEOS)is used as a cross-linking agent to improve its mechanical strength.The results show that this adhesive has excellent underwater adhesion properties and can achieve adhesion to various substrates.At the same time,the drying temperature has a greater influence on this adhesive,and the higher the temperature,the greater the adhesion strength.