Preparation And Properties Of Multifunctional Composite Hydrogels With High Mechanical Strength

Hydrogel is a kind of soft materials with three-dimensional network, which is widely used in the field of daily life, industrial supplies, biological tissue engineering, biological cell immobilization and drug release. Moreover, preparation and application of functional and intelligent hydrogel is a hot topic in the field of polymer science. In this thesis, two kinds of functional composite hydrogel have been successfully prepared by different methods. The structures, properties such as biological activity, multiple stimuli-responsive and potential applications of composite hydrogels have also been discussed. The main contents are as follows:The high strength anisotropic poly(vinyl alcohol)(PVA) hydrogel was prepared by cycle directional freezing-thawing(DFT) method. Then, the mechanical properties, water content and anisotropic microstructure of obtained hydrogel were studied. The results showed that the PVA hydrogels had typical anisotropic porous-channel microstructures determined by SEM; water content exceeded 85%; and the mechanical properties increased with the increase of cycle DFT number and PVA concentration. In addition, poly(lactic acid-co-glycolic acid)(PLGA) microspheres loaded bovine serum albumin(BSA) was prepared by modified double emulsions method. The release kinetics of BSA was studied. The results showed that BSA could be encapsulated into the PLGA microspheres, and the encapsulation efficiency increased with the decrease of the PLGA microspheres size.The anisotropic PVA/BSA-loaded PLGA microspheres composite hydrogel was obtained by cycle directional freezing-thawing(DFT) method. The SEM result suggested that PVA hydrogel had anisotropic microstructure and PLGA microspheres dispersed in the anisotropic channel of PVA hydrogel. Compared to bare PVA hydrogel, the compression strength of composite hydrogel decreased slightly. The adhesion and proliferation of chondrocytes in the composite hydrogels were further investigated. The fluorescence microscopy and SEM results showed that the adhesion and proliferation of chondrocytes on the anisotropic composite hydrogels could be significantly improved by the BSA-releasing microspheres and the chondrocyte had an anisotropic distribution.The multiple stimuli-responsive nano-composite hydrogels with dual network were prepared by in situ-radical polymerization of N-isopropyl acrylamide(NIPAM) and acryloyloxyethyltrimethyl ammonium chloride(DAC) in the aqueous solution of Laponite RDS with a minute amount of N, N′-methylenebisacrylamide(MBA). The dual network of hydrogel were constructed by N, N’- methylene acrylamide(MBA) and clay. The swelling properties of prepared hydrogels could be regulated by changing clay concentration and chemical crosslinking agent content. Meanwhile, the elongation could reach 240% with the tensile strength 400 KPa, and the largest compressive deformation could reach 98% with the compression strength 5MPa. Furthermore, the composite hydrogels showed sensitive to stimuli, such as temperature, ion concentration and electric field. The composite hydrogels had significant temperature-responsive, and the responsive range could be regulated by DAC monomers. Simultaneously, the composite hydrogel also showed an oscillatory swelling-shrinking behavior in response to ion concentration and an electrically driven response capability.