Preparation And Properties Of Surface-active Ionic Liquid/polyacrylamide Hydrogel

Hydrogel is a kind of polymer material with three-dimensional network structure,which swells in water but does not dissolve.It has gradually played an irreplaceable role in tissue engineering,agricultural moisturizing,cartilage repair,drug delivery and other fields.However,the poor mechanical properties of conventional org+anic crosslinked hydrogels limited hydrogels’application scope in production.Hydrophobic association modification is an effective way to improve the performance of hydrogels,which has attracted researchers’attention in recent years.Ionic liquids,which have a characteristics of low vapor pressure,good thermal stability and excellent electrical conductivity,can be designed to adjust their performance by changing anions and cations.Ionic liquids are expected to be used as crosslinkers for the construction of hydrophobic associated hydrogels with improved properties.In this paper,a hydrophobic association hydrogel C_n-PAM with high strength and toughness was prepared using a new designed ionic liquid with high surface activity 3-vinyl-1-（dodecoxycarbonylmethyl）imidazole bromide[C₁₂E_mVI_m]Br as crosslinking agent.The surface morphology,mechanical properties,swelling property and dye adsorption property were investigated.The prepared hydrophobic association hydrogels have smoother and more uniform surface and stronger mechanical properties.When the concentration of[C₁₂E_mVI_m]Br was 0.48 mmol·L^-1,C_n-PAM hydrogel shows the best mechanical properties with the tensile stress of 258 k Pa and optimal elongation at break of 2554%,which was 9.9 and 8.5 times that of MBA/PAM hydrogel,respectively Furthermore,the mechanical properties remain stable after six times cyclic stretching.Using C_n-PAM hydrogel,the maximum adsorption capacity was 88 mg·g^-1 for methyl orange,and the adsorption behavior fitted the Langmuir equilibrium model and the pseudo-second-order kinetic model.In order to further improve the mechanical properties of hydrophobic association hydrogels,double network hydrogels were prepared by introducing the coordination system of acrylic acid and iron ion as the second network.The hydrogel showed a smooth,uniform surface structure with almost no pores.When the concentration of crosslinking agent[C₁₂E_mVI_m]Br was 0.24 mmol·L^-1,the dosage of acrylic acid was 0.5 g,and the concentration of ferric chloride was 0.15 mmol·L^-1,the tensile strength of the double-network hydrogel can reach 2.7 MPa,which is 85.7 times that of the C₀-PAM chemical cross-linked hydrogel.Meanwhile,the tensile fracture rate of the double-network hydrogel can be maintained at more than 800%,showed a strong mechanical properties.It shows strong mechanical properties.The hydrophobic association double network hydrogels also show p H resistance,and can maintain a high strength30 times higher than that of MBA chemical cross-linked hydrogels in extreme p H environment for a long time,which provides a research idea for the synthesis of new hydrogels and the development of special applications of hydrogels.