Preperation And Properties Of Multi-Stimuli Responsive Magnetic Hydrogel And Liquid Metal-Incorporated Organic Aerogel

Gel is a dispersion system with porous network structures formed by interconnecting colloidal particles or polymers,and its porous structure is filled with the dispersion medium.According to the different types of dispersion medium,gel materials can be divided into hydrogel,aerogel,organogel and so on.In recent years,smart gel materials have attracted extensive scientific attentions due to the stimuli-responsive characteristics.Particularly,smart hydrogel and organic aerogel materials have good application prospects in the fields of drug delivery,biosensors and soft actuators.Recently,smart magnetic hydrogels have been widely applied in targeted drug release,environmental monitoring,DNA extraction,immunoassay,novel coatings,organic/biochemical synthesis due to their magneto-responsive properties and abundant surface functional groups.However,most of the current researches focus on these magnetic hydrogel systems with stable chemical crosslinking networks and pharmaceutical applications.In this work,a multi-stimuli responsive magnetic hydrogel with excellent dispersion stability is prepared through solvent transfer and hydrophobic self-assembly by using oleic acid-coated Fe₃O₄ nanoparticles as the magnetic nanoparticles and the amphiphilic penta-block copolymer-based aqueous solution as the carrier fluid.The magnetic hydrogel material behaves as a liquid fluid with a low viscosity at room temperature,and can flow freely under the traction of magnets without solid-liquid separation.Under external stimulation（light,heat,alternating magnetic field）,the magnetic hydrogel can be transformed from a low-viscosity sol state to a high-viscosity gel state.In addition,the phase structure,magnetic and rheological properties of the magnetic hydrogel are investigated by NMR spectrometer,FT-IR spectrometer,X-ray diffractometer,transmission electron microscope,vibrating sample magnetometer and rheometer.The results show that the magnetic hydrogel has a core-shell structure with a diameter of 23 nm and the maximum magnetic saturation intensity is 6.67 emu/g,which exhibits superparamagnetism.Besides,the viscosity is 0.1 Pa·s at 20℃,while it can be as high as 1.3×10³ Pa·s at 40℃.The storage modulus G’（0.022Pa）at 20℃was much lower than that（10000 Pa）at 40℃.All in all,the viscosity and modulus increase with the increase of temperature,and the magnetic hydrogel can undergo a sol-gel phase transition with a complete gelation temperature of 40℃.Furthermore,we also explore the new applications of the magnetic hydrogel in moveable valves,damping materials and other fields in this work.As a unique organic aerogel material,shape-memory organic aerogel not only has the porous structure,excellent mechanical properties and environmental stability of traditional organic aerogel,but also has the characteristics of restoring the initial shape under external stimulation.The aerogel materials present potential application prospects in aerospace,intelligent fiber,flexible actuator,biomedicine and other fields.However,there are few reports on shape memory polymer aerogel materials until now.In this work,a kind of liquid metal-incorporated organic aerogel with shape memory is successfully prepared by introducing liquid metal into organic aerogel materials.The ratio of monomer/crosslinking agent/chain extender/liquid metal and drying methods for the liquid metal-incorporated organic aerogel are explored herein.The liquid metal-incorporated organic aerogels are characterized by FT-IR spectrometer,specific surface area analyzer,scanning electron microscope,true density analyzer,dynamic mechanical analyzer and etc.,and the microstructure,porosity,mechanical properties and shape memory performance are investigated.These results demonstrate that the internal morphology of the aerogel is a large porous structure with random aggregation of particles,and the porosity is 78%.With the increase of the mass concentration of liquid metal,the mechanical properties of the liquid metal-incorporated organic aerogel are enhanced and the maximum elastic modulus reaches 0.85 MPa.In addition,the liquid metal endows the organic aerogel with conductivity,which gradually improves with the increase of liquid metal content.Simultaneously,the shape-memory property of the organic aerogel is not affected.The liquid metal-incorporated organic aerogel can gradually return to the original shape with a recovery rate of ca.70%after a 30%compression.These excellent properties make the material promising for applications in sensors,smart actuators and other fields.