Construction Of Hyperbranched Self-adaptive Network And Its Broad-spectrum In-situ Adhesion On Wet/underwater Surfaces

In applications such as industrial manufacturing,underwater in-situ assembling and biological tissue repairing,adhesives are required to produce rapid and reliable adhesion strength with substrates in wetted/submerged environments.In these applications,the interfacial water on the substrate surfaces prevent the contact with the adhesives polymer chains weaking the molecular interactions and avoiding the generation of the"glue nail"structure,which dramatically reduced the adhesion strength between the surface and the adhesives.At the present,the polymer chain segment through the‘diffusion–contact’mechanism can pass through the interface water layer and the substrate to form inter-molecular force.At the same time,adhesion strength is also able to be generated through the‘dry gel fast hydration’or‘hydrophobic repulsion’.However,the mentioned mechanisms have the disadvantages such as long effective time,limited substrate types,high toxicity,irreversibility and demanding environmental conditions,which make it difficult to appeal the practical requirements.In this thesis,N,N’-methylenebis(acrylamide)(MBA)and 4,4’-diaminodicyclohexylmethane(HDDM)were used as the hydrophilic/hydrophobic monomers respectively,and a serials of hyperbranched polymers(PM-H)were designed and fabricated.PM-H polymer had abundant internal hydrogen bonds.And the hydrophobic chains were able to aggregate and form the physical cross-linking structures,forming a hydrogel,which could quickly hydrate eliminating the interfacial water layer,enabling the rapid contact between the adhesive with substrates in wet/submerged environments.The hyperbranched structures of PM-H gave hydrophilic/hydrophobic chain segments the ability to move freely within restricted intervals,avoiding the macroscopic phase separation.At the same time,the self-adaption network was able to boom the intermolecular interactions with the substrate,endowing the adhesives the broad-spectrum adhesion ability towards variety types of substrates.This thesis designed and prepared a serials of PM-H polymers with different molecular weights and branching degrees by tunning the ratio between the hydrophilic/hydrophobic monomers,and studied their thermomechanical,rheological,swelling and dissolution properties,characterized their adhesion strength to ceramics,wood,aluminum,polyethylene,glass and other substrates underwater,investigated the relationship between temperature and salinity on the bonding performance of the materials,and conducted a preliminary application in biomedical fields.PM-H polymers were used as bioadhesive in this thesis,and the adhesive strength,the ex-vitro cytotoxicity,the antibacterial ability and the ex-vitro blood toxicity were evaluated.The conclusions of this thesis are listed as below:1.The molecular weight and branching degree of PM-H can be controlled by changing the ratio of MBA to HDDM monomer.In this paper,the molecular weight of PM-H can be controlled from 2.7381×10~6-9.5833×10~7,and the branching degree can be varied from 0.4-0.5.The glass transition temperature of serialized PM-H polymers is 20-71℃,and the room temperature energy storage modulus is 4-8 MPa.2.PM-H hydrogels are able to rapidly evolve adaptively to the external environment.After five minutes of immersion in pure water,the surface contact angle decreased from 28.9°to 51.7°,while after five minutes of immersion in liquid paraffin,the contact angle increased from 98°to 110.8°.XPS results showed an increase in the elemental N content of the surface when immersed in water,much higher than the characteristic absorption peaks of the unimmersion and immersion in polar solvents.3.PM-H hydrogel can achieve broad-spectrum rapid bonding with multiple substrates in underwater environment.The maximum tensile shear strengths of serialized PM-H hydrogels were 3.5 MPa,218 k Pa,282 k Pa,205k Pa,195 k Pa,and 230 k Pa after 1 minute of contact with wood,glass,aluminum,polyethylene,polypropylene,and ceramic surfaces underwater,meanwhile,results show that temperature and salinity do not have a significant effect on the underwater bonding ability of PM-H hydrogel.4.PM-H hydrogel has excellent bioadhesive ability.In vitro cytotoxicity showed that the leachate of PM-H hydrogel had no significant effect on the survival rate of mouse epithelial fibroblasts(L929 cells),in addition,the hyperbranched structure with a large number of terminal amino groups gave PM-H hydrogel a broad-spectrum antibacterial ability,but have a certain toxicity to its red blood cells,will cause the rupture of red blood cells,so it needs to be further modified in order to be used in the body.