The Preparation And Performance Study On High Strength Hydrogels Based On Hydrophobic Association And Hydrogen Bond

Hydrogels are generally formed by a three-dimensional hydrophilic polymer network,which has both the fluidity of liquids and the elasticity of solids.It can absorb a lot of water without dissolving while maintaining a certain shape.Owing to its wet-soft properties,it has received extensive attention in the fields of drug delivery,sensors,soft electronics,water treatment,etc.However,traditional hydrogels often suffer from poor structural stability,weak mechanical properties,and inability to self-heal after fracture,which largely restrict their applications.Therefore,designing a hydrogel with novel structure,excellent mechanical properties and self-healing ability is the purpose of this paper.In order to achieve this goal,we intend to introduce hydrophobic association and hydrogen bonds into the hydrogel to establish a new energy dissipation mechanism.Under the action of external force,the hydrophobic association and the disintegration of hydrogen bonds dissipate a large amount of energy,thereby improving the toughness of the hydrogel.When the external force is removed,since both hydrophobic association and hydrogen bonding are dynamically reversible,their reformation is expected to endow hydrogels with self-healing properties.Based on the above,this paper conducts the following research:（1）The hydrophobic monomers dodecyl vinyl imidazolium bromide（DVI）and octadecyl vinyl imidazolium bromide（OVI）were synthesized.The traditional hydrophobic monomers need surfactants to solubilize,but the hydrophobic monomers synthesized in this paper have a molecular structure similar to cationic surfactants,which makes them able to react with N-methylol acrylamide（NMA）and acrylamide（AM）under more different conditions to prepare dual-physical crosslinked hydrogels.Specifically,the effects of changing the molar ratio between the hydrophobic monomer and the hydrophilic monomer on the coagulation of the system under various conditions such as no surfactant,nonionic surfactant,ionic surfactant and anionic monomer were studied.The effect of glue performance.After that,we explored the effects of fixing the content of hydrophobic monomers and hydrophilic monomers,changing the concentration of surfactants on the properties of the gel,and exploring the properties of N-methylol acrylamide and acrylamide monomers alone to form hydrogels.Condition.Finally,a series of performance tests were carried out on the prepared gel,so as to know the influence of the length of the alkyl chain of the hydrophobic monomer,the type of the hydrophilic monomer and the ratio between the two on the performance of the gel.（2）The experimental results show that the Q₅（DVI-co-AM）hydrogel prepared without surfactant has a tensile strain of 25.8 mm/mm,a tensile stress of 1.11 MPa,and a fracture energy W of 11.53 MJ/m³.The P₅（OVI-co-AM）hydrogel prepared without surfactant has a tensile strain of 15.87 mm/mm,a tensile stress of 1.30 MPa,and a fracture energy W of 10.02 MJ/m³.The P₆（OVI-co-AM）hydrogel prepared with nonionic surfactant exhibited a tensile strain of 21.34 mm/mm,a tensile stress of 1.15MPa,and a fracture energy W of 13.13 MJ/m³.The P₇（OVI-co-AM）hydrogel prepared with ionic surfactant has a tensile strain of 10.86 mm/mm,a tensile stress of 1.50 MPa,and a fracture energy W of 9.77 MJ/m³,these four hydrogels belong to the range of high-strength hydrogels.It can be seen from the above that the length of the alkyl chain of the hydrophobic monomer,the type of the hydrophilic monomer and the ratio between the two have a great influence on the performance of the gel.Among them,the higher the degree of hydrophobicity,the tighter the crosslinking density of the gel,the better the mechanical properties,and the more advantages of acrylamide compared to N-methylol acrylamide.The excellent mechanical properties of these four gels are also closely related to the cooperative energy dissipation of various non-covalent physical forces.The performance test results of the gel are as follows:it can be seen from the infrared test that the reaction between the monomers forms a gel,and the prepared gel is subjected to tensile testing to obtain four high-strength gels of Q₅,P₅,P₆,and P₇.The four gels were tested more comprehensively,and the rheological results further indicated that the gels were formed and possessed good elasticity.Swelling tests show that the swelling ratio depends on the hydrophilicity and crosslink density of the network.Self-healing tests suggest that the healing ability of the hydrogel may be related to the healing temperature as well as the mobility of the polymer chains.In summary,the cationic hydrophobic monomers OVI and DVI can be used for the construction of high-strength hydrogels,and have good adaptability to surfactants.The prepared hydrogels have high tensile strength and good stability.As well as the advantages of no need to add chemical cross-linking agents,these results provide a new idea for the preparation of hydrophobically associating hydrogels.