Preparation And Electrochemical Properties Of Ionogel Based On Dendritic Polymers

Compared with the traditional gel polymer electrolyte?GPE?based on carbonate ester,ionogels have recently received a great deal of attention for use in many various electrochemical devices,such as supercapacitor and lithium-ion batteries,due to their good flexibility,easy processing,high thermal stability,high ionic conductivity,nonflammability,and no explosion.However,most of the matrix polymers of the ionogels are linear polymers,which have some disadvantages such as high glass transition temperature and few functional groups,resulting in lower electrical and mechanical properties.Therefore,it is urgent to find a new type of polymer as the matrix to improve the performance of the ionogel,which has low glass transition temperature and lots of functional groups.In our paper,novel ionogels based on dendritic polymers?dendrimer and hyperbranched polymer?have been prepared by using physical and chemical cross-linking methods,and their phase behavior,rheological,electrical,mechanical and self-healing properties were also systematically studied.The results are as follows:?1?Temperature-sensitive ionogels based on hydroxyl terminated hyperbranched polyester?H20P/H40P?were prepared by a simple physical mixing method.The hydroxyl terminated hyperbranched polyester were dissolved in the[BMIM][BF₄]ionic liquid.The phase separation,gelation behavior and electrochemical performance were studied.It is found that the physical ionogel system exhibits typical upper critical solution temperature phase behavior with temperature change,and the phase transition temperature increases first and then decreases with the increase of polymer content.The phase transition temperature of H20P system is higher than H40P system.The rheological results show that the sol-gel transition concentration of the system is about 20%,and the ionogel modulus increases with the increase of the polymer content,which can reach 10⁵ Pa.Electrochemical test results show that the room temperature ionic conductivity of all obtained ionogels is above 1.0×10^-4 S/cm,indicating that the ionogel has excellent ionic conductivity.?2?A novel self-healing ionogel with dynamic reversible bonds of boron ester was prepared by dehydration condensation of 1,4-benzenediboronic acid and hydroxyl terminated hyperbranched polyester in an ionic liquid.The POM results show that the ionogel possess superior self-healing properties and it can completely repaired within 1 h.The rheological test result shows that the gel-sol transition temperature of the self-healing ionogel is between110-150 ^oC,and the transition temperature of the ionogel increases with the increase of the polymer content.The prepared ionogel has good thermal stability with decomposition temperature of more than 200 ^oC.?3?Self-healing ionogel with the dynamic covalent bonds of acylhydrazone was prepared by Schiff base reaction of the terminal amino group on dendritic polyamide-hydrazide?PAMAM-h?and the pyruvic aldehyde in the ionic liquid of[EMIM][OAc],and the pyruvaldehyde was used as the crosslinking agent.The microscopic dynamic repair process of the ionogel was observed under a polarizing microscope,and it was confirmed that the obtained ionogel has excellent self-healing properties.The oscillatory shear measurement results show that the modulus of the ionogel increases with the increase of PAMAM-h content,and that the modulus also increased with the increase of generation.The ionic conductivity of all ionogels increases monotonically with increasing temperature.