Preparation And Study Of Fully Physical Crosslinked Nanoparticle/Polymer Composite Hydrogel

Poly（N-isopropylacrylamide）（PNIPAm）hydrogel has excellent biocompatibility,temperature sensitivity and other properties,so it has potential application value in fields such as tissue engineering and wearable sensors.However,the application of chemically crosslinked PNIPAm hydrogels is always limited by their poor mechanical properties.In the work of this paper,we introduce the nanoparticle and double network structure into the PNIPAm hydrogel system through hydrogen bond interaction and ionic interaction to enhance the mechanical properties of the hydrogel,and give the PNIPAm hydrogel fluorescence and self-recovery and other performance.First,spherical carbon quantum dot nanoparticles（C-dots）and sheet-like lithium algae nanoparticles（clay）were selected as cross-linking points and reinforcing agents.C-dots-clay-PNIPAm hydrogel was prepared by in-situ polymerization of N-isopropylacrylamide in aqueous dispersions of C-dots and clay.The internal microstructure of the C-dots-clay-PNIPAm hydrogel was observed by scanning electron microscopy（SEM）.The effects of the amount of carbon quantum dots and lithium algae nanoparticles on the mechanical properties of hydrogels were investigated by tensile test and rheological test.The self-healing properties were analyzed by tensile testing of the self-healing C-dots-clay-PNIPAm hydrogel after cutting.The effects of temperature on the equilibrium swelling ratio and fluorescence properties of hydrogels were also investigated.The results show that C-dots-clay-PNIPAm hydrogel has high mechanical strength and super-stretching properties.Spherical C-dots and sheet-like clay have synergistic effects on the mechanical properties of hydrogels.C-dots-clay-PNIPAm hydrogels are self-healing and temperature sensitive.At a volume phase transition temperature of around 34℃,the hydrogels undergoes a swelling-deswelling reversible transition,and fluorescence effect appears-disappears reversibly transition.The second part of the work,through the lithium algae-polyacrylamide（PAM）network as the first network,Fe³⁺-sodium alginate（Alginate）network as the second network to prepare lithium algae-polyacrylamide/Fe³⁺-sodium alginate(Clay-PAM/Fe³⁺-Alginate)double network hydrogel.The effects of clay content,sodium alginate content,acrylamide content and Fe³⁺concentration on mechanical properties,self-recovery properties and anti-fatigue performance of clay-PAM/Fe³⁺-Alginate double-network hydrogels were investigated by tensile test and tensile-recovery test.The microstructure of Clay-PAM/Fe³⁺-Alginate double-network hydrogel was characterized by SEM.The pH responsiveness of the hydrogel was investigated by testing the equilibrium swelling of the hydrogel in different pH solutions.The results show that the Clay-PAM/Fe³⁺-Alginate dual-network hydrogel has super-stretching,high-strength mechanical properties,good fatigue resistance,and pH responsiveness.