Preparation And Wet Adhesion Of Water-triggered Amphiphilic Hyperbranched Polymer Adhesives

In recent years,wet adhesives have found wide applications from marine industry to biomedical fields.However,the interfacial hydration film and continuous water erosion in wet and aquatic environments can severely impair the interfacial bonding.Therefore,achieving strong and long-term wet adhesion remains a great challenge.Although mussel-inspired catechol-based wet adhesives display good wet adhesive properties,most catechol-based adhesives are easy to suffer from oxidation and excessive consumption of catechol groups during the crosslinking process,making it difficult to achieve efficient and long-term wet adhesion.To solve the above problems,the combination of water-triggered solidification,strong hydrophobic interactions and abundant catechol groups was achieved via one-step Michael addition reactions of rigid and hydrophobic polyvinyl monomer,divinyl monomer and dopamine hydrochloride（DOPA）to construct a series of water-triggered amphiphilic hyperbranched polymer wet/underwater/tissue adhesives.Then their adhesive mechanisms,adhesive properties,environmental adaptability and on-demand debonding performance were further investigated.The main research contents and results were as follows:（1）A series of isocyanurate（IC）based amphiphilic hyperbranched polymer wet adhesives were prepared by one-step Michael addition reactions of the rigid and hydrophobic tris（2-acryloyloxyethyl）isocyanurate（TAC-IC）,divinyl monomer and DOPA.Without the addition of oxidant or metal ions,the adhesives can undergo water-triggered spontaneous solidification and wet bonding through shrinkage and aggregation of rigid and hydrophobic components.As the hydrophobicity of the divinyl monomer increased,the hydrophobicity and water-resistant adhesive properties of the adhesive were enhanced.Low molecular weight divinyl monomers were beneficial to increase the density of terminal adhesive groups,thereby enhancing adhesive properties.The adhesives possessed universal in air/water-resistant adhesive ability,and exhibited strong adhesive performance to metal,inorganic non-metallic and polymer substrates（including low surface energy PE）.The in air/water-resistant adhesive strength to substrates achieved high values of 2018.7 and 1136.4 k Pa,respectively.The adhesives also exhibited repeatable adhesive performance,and the maximum retention rate of in air repeatable adhesive strength were as high as 85.9%.In addition,the IC-based hyperbranched polymer adhesives can also be applied for underwater adhesion.（2）A series of POSS-based amphiphilic hyperbranched polymer underwater adhesives（adhesive I）were constructed via Michael addition reactions between the potent rigid hydrophobic and terminally multifunctional octa-acrylosilasesquioxane（AC-POSS）with divinyl monomer and DOPA,and further self-assembled into adhesives II with POSS clusters under the synergistic effect of the sharply reduced solubility of the POSS cage and the aggregation effect of multifunctional groups,thereby enhancing the hydrophobicity and cohesion of the adhesives.Under water contacting,the adhesives I and II can coacervate and solidify to remove the moisture at the interface,promoting the catechol groups exposure and resulting in tight contact and eminent under adhesion between the adhesive and diverse materials.The underwater adhesive strength to PE and PTFE with low surface energy can reach 340.4and 191.4 k Pa.The hydrophobic protection of the rigid and hydrophobic component endowed the adhesives with outstanding resistance to oxidation and water erosion,thus adhesive II exhibited excellent adhesive properties in a variety of aqueous environments（such as PBS solution,artificial seawater,and aqueous solutions with p H range from 3 to 11）.Furthermore,adhesive II revealed remarkable repeatable adhesion and long-term adhesion.（3）A cytocompatible and injectable bioadhesive was prepared via Michael addition reaction of rigid and hydrophobic octa-acrylosilasesquioxane（AC-POSS）,bioreducible N,N’-bis（acryloyl）cystamine,N-acryloxysuccinimide and DOPA.Bioadhesive can achieve wet adhesion to biological tissue through the synergistic effect of topological entanglement,catechol chemistry and covalent bonding.The adhesive strengths enhanced with the extension of adhesive time.When the curing time was 24h,the adhesive strength to porcine skin reached a high value of 135.1 k Pa.In the early stage of tissue adhesion,the bioadhesive had repeatable adhesive performance in the range of 35.7±8.4 k Pa,which was beneficial to deal with the secondary dehiscence of the wound.Treatment of biocompatible 0.5 M Na HCO₃ and 10 m M DTT in PBS solution can simultaneously reduce the cohesion and adhesion of the bioadhesive,resulting in a sharp drop in adhesive strength and noninvasive on-demand debonding.