Preparation And Properties Of Stimuli-responsive Coordination Polymer Gel Based On Azopyridine Ligand

In recent years,smart materials with self-healing and multiple stimulus-response properties have attracted more and more attention.Especially metal coordination polymer gel is widely used as a new type of reactive material due to its’ high metal content and fast external response speed.Therefore,it has great application potential in the fields of intelligent response materials,sensors,and drug delivery.To further investigate the assembly process and stimulation response of the coordination polymer gel,a novel coordination polymer gel based on azopyridine ligand was synthesized,and its multiple stimulus responsiveness was studied.The main research contents:First,two types of C3 symmetric azopyridine ligands were synthesized successfully:tris(4-(3-pyridylazo)phenyl)benzene-1,3,5-tricarboxylate(ligand D)and tris(4-(4-pyridylazo)phenyl)benzene-1,3,5-tricarboxylate(ligand Z).And then the two ligands were coordinated with Ag(I)to prepare the coordination polymers Ag D and Ag Z with azo groups on the main chain.The conditions of gel formation of two coordination polymers were explored utilizing the control variable method.The research results show that Ag Z cannot form a gel;the solvent for Ag D to form a gel can be DMF or DMAc,and the minimum gel concentration is 0.33% and 0.45%,respectively.The ratio of metal ion to the ligand can form a gel in a wide range greater than 1.Second,the driving force and formation mechanism of Ag D gel was characterized by XRD,IR,rheology,UV-Vis,and so on.The morphology of Ag D gel and Ag Z precipitation was analyzed by TEM and SEM.The effect of molecular structure on gel formation was discussed,and the coordination between metal-ligand coordination and π-π stacking effect was demonstrated to play a key role in the formation of gels.Finally,by adjusting the external stimulus conditions,such as temperature changes,mechanical shock,chemical substances introduction,ultraviolet-visible light irradiation,we observed the response behavior and self-repairing ability of Ag D coordination polymer gel.Through the above experiments,the multiple stimuli response of the coordination polymer gel is proved,and the change of its assembly structure is the basis of the gel responsiveness.