Preparation And Application Of High Tenacity Polyvinylalcohol/Sodium Alginate Magnetically Responsive Hydrogels And Polyacrylamide-based Electrically Conductive Responsive Hydrogels

With the emerging field of flexible smart machines being developed rapidly,there has been a trend to investigate the use of hydrogels as key components of devices and machines to replace or supplement many traditional machines based on rigid materials.Hydrogels can be modified by adding functional groups,additives or nano-fillers,and the modified hydrogels have great advantages in replacing traditional rigid machines.However,the fragility and poor deformability of hydrogels currently limit their application.Therefore,the design of hydrogels with sufficient intelligence and effective configuration of mechanical properties is crucial for the development of hydrogel-based soft machines.In this thesis,magnetic nano-Fe₃O₄is used as an additive to dope the hydrogel to prepare a high-strength smart magnetically responsive hydrogel.Based on this study,another highly flexible conductive electromagnetically responsive hydrogel is prepared using a conducting polymer polypyrrole wrapped on the Fe₃O₄surface for performing smart response tasks,and the main research is as follows:1.The magnetically responsive hydrogel material was prepared by doping Fe₃O₄functionalized with citric acid in sodium alginate/polyvinyl alcohol hydrogel,and then the Hofmeister effect was introduced to turn the fragile hydrogel into a high-strength hydrogel by immersion in 1.3 M Sodium citrate solution as well as cyclic freezing-thawing.The optimized hydrogel had a modulus of fracture of 6.66 MPa at 282%strain and a modulus of rupture of 6.66 MPa,Young’s modulus of 2.51 MPa,and toughness of 9.31 MJ m^-3at 282%strain,and the mechanisms of Hofmeister effect and cyclic freezing-thawing on the mechanical properties of the hydrogel were discussed in detail.Exploring the application of hydrogel materials in soft robotics through shape deformation of magnetically responsive smart hydrogels prepared by magnetic field control as well as swimming。2.The functional Fe₃O₄ coated with the conductive polymer polypyrrole and doped in the polyacrylamide hydrogel network to fabricate a conductive electromagnetically responsive hydrogel material with high flexibility,and the effects of monomer concentration and doping amount on the mechanical properties of the hydrogel were explored.The optimized hydrogel had a strain of up to 961.2%,an elastic modulus of 87.8 KPa,and a toughness of 1010.5 KJ m^-3.A flexible sensor was prepared using the hydrogel,and applied to the monitoring of human joint and throat muscle signals,and the ability to monitor magnetic field changes was explored.