Preparation And Properties Of CoFe₂O₄ And CoFe₂O₄/Fe³⁺/PAA Magnetic Hydrogels

Co Fe₂O₄ is a magnetic material with excellent performance,which is added to PAA hydrogel to prepare magnetic hydrogel with fast response in magnetic field.In this paper,hydrophilic Co Fe₂O₄ particles are prepared and added to hydrogel to prepare magnetic hydrogel,and its structural properties are analyzed,and the effect of the addition amount of Co Fe₂O₄on the self-healing performance of magnetic hydrogel under the action of magnetic field is investigated.The effect of Co Fe₂O₄ addition on the self-healing properties of magnetic hydrogels was investigated.Firstly,Co Fe₂O₄ magnetic particles coated with surfactant diethanolamine（DEA） were prepared by co-precipitation method in this experiment,and the synthesized Co Fe₂O₄ particles were characterized by Fourier infrared spectroscopy（FTIR）,transmission electron microscopy（TEM）,X-ray diffractometer（XRD）and hysteresis line analyzer.The results show that the hydrophilic Co Fe₂O₄ magnetic particles with a particle size of about 190 nm were successfully synthesized and uniformly dispersed in aqueous solution,indicating their good hydrophilicity.The results of the magnetic test indicate that the Co Fe₂O₄ particles with spinel structure have good ferromagnetism,which also proves that the Co Fe₂O₄ particles have good magnetic responsiveness in the magnetic field,and the prerequisite for the preparation of magnetic hydrogel is that the Co Fe₂O₄ particles have hydrophilicity and magnetic responsiveness.Next,Co Fe₂O₄ particles were mixed with acrylic acid（AA）monomer by the encapsulation method,and the initiator was added to induce polymerization to form magnetic hydrogels,and the structural properties of the magnetic hydrogels were analyzed by FTIR,film stretching tester,thermal weight loss analysis（TGA）,and dynamic thermomechanical analysis（DMA）.The results show that the prepared magnetic hydrogels have good magnetic responsiveness,and the addition of Co Fe₂O₄particles also improves the thermal stability,tensile strength,and energy storage modulus of the magnetic hydrogels,because the Co Fe₂O₄ particles are uniformly distributed in the three-dimensional network structure of the hydrogels leading to the improvement of the mechanical properties of the hydrogels,but because the Co Fe₂O₄particles occupy the three-dimensional network in the magnetic hydrogels space,which reduces the water content in the hydrogel and leads to a decrease in the swelling of the hydrogel.Finally,the effect of Co Fe₂O₄ particles on the self-healing of the hydrogel under the action of magnetic field was analyzed.The tensile strength of the fractured magnetic hydrogel was tested after a certain time of repair in the magnetic field,and the repair effect was judged by comparing with the original tensile strength.The results show that Co Fe₂O₄ particles can greatly improve the self-healing performance of the hydrogel under the action of magnetic field.There are two main factors:（1）Co Fe₂O₄ particles are distributed in the three-dimensional network of the hydrogel,in the presence of magnetic field,Co Fe₂O₄ particles will vibrate,thus driving the hydrogel entanglement of the PAA main chain at the section,which in turn increases the interaction of the broken hydrogen bonds with the hydroxyl or carboxyl groups in the hydrogel,accelerates the formation of hydrogen bonds.At the hydrogel section,the vibration of magnetic particles drove the entanglement of PAA backbone at the section and the flow of Fe³⁺with carboxyl groups on PAA backbone,which interacted to form dynamic ionic bonds and thus greatly improved the self-healing rate.